Clarity in Technical Reporting

8/3/2019 Clarity in Technical Reporting

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NASA SP-7010

CLARITY INT E C H N I C A L REPORTING

by S. KatzoffLangley Research Center

Second Edition

Scientific and Technical Information Division 1964NATIONAL AERONAUTICS A ND SPACE ADMINISTRATION

Warhington, D.C.


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Second printing, 1965Third printing, 1968Fourth printing, 1973

F O R S A L E B Y T H E S U P E R I N T E ND E N T O F D O C UM E N T S , U.S. G O VERNM ENT PR I NT I NGO FFI CE , WASHI NG TO N, D .C . 20402. PRI CE 35 CENTS. DO M ESTI C PREPAI D: 25 CENTS,G PO BO O KSTO RE STO CK NUM BER 3300-00513


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FOREWORDWith the sharp increase in recent years of the volume of

technical reports in aerospace fields, it has become even moreimportant for report authors to present their materialclearly and concisely. This booklet, which offers common-sense suggestions for improving written and oral reports, isdesigned not only for prospective writers within the NationalAeronautics and Space Administration but also for scientistsand engineers among the agency's contractors who mustreport the results of their research.

The history of this booklet is that of a publication thatdid not set out t o be one, but tha t has been virtually forcedinto print by the demand of would-be readers. For a num-ber of years prior to and since the initial printing, the author,a busy scientist at the Langley Research Center, has actedas counselor to fresh-out of-college youngsters coming towork a t the Center-guiding these inexperienced authors inthe art of writing technical reports that measure up toLangley's exacting standards. In 1955, Dr. Katzoff, con-vinced of a widespread need far practical pointers on technicalwriting, put some of his thoughts on the subject on paper.Typed and duplicated in small numbers, this highly informaldocument was classed as a Langley internal paper.

But publications, notably the best ones, have a life oftheir own quite separate from-the intentions of their authors.Soon "Clarity in Technical Reporting? began to earn aword-of-mouth reputation as a small clkssic. Several timescopies became scarce, and were run off in small amounts,and became scarce once more. Meantime Langley, actingas a kind of seedbed for its rapidly expanding parent agency,


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sent many of its alumni to other NASA Research Centers,and thus treasured personal copies were carried to otherlocations, there to repeat similar cycles of modest reproduc-tion and scarcity.

When this curious spread of an elderly informal docu-men t was discovered, this Division concluded that so prizedand useful a paper merited better treatment. In fairness toits author, now Senior Staff Scientist of the Langley ResearchCenter, one should note th at he had no intention of appearingin print as an authority on technical writing. Instead, thisbooklet should be read as what i t is: counsel for those who maywish i t from a man who has read-and written-many tech-nical papers.

MELVIN. DAY,DirectorSc ien ti f ic and Technica l In fo rm a ion Division


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INTRODUCTIONTHERATE OF PRODUCTION of technical reports is now so

high that the typical research worker is continually frus tra tedin his desire to keep informed of other workers' progresswhile working effectively on his own problem. His pre-dicament is made worse by the fact tha t many of th e reportsthat he must read are so ineptly written that the effortrequired t o assimilate them is several times as much as theircontents should require. Th e monetary cost of this ad -ditional effort is certainly an appreciable fraction of thetotal cost of research and development, while the hindranceto our nation's scientific progress may be of crucialimportance.

The basic reasons for lack of clarity are sometimesdifficult to identify,' and no doubt vary from one author toanother. Work with inexperienced authors has indicated,however, that they generally do not have ineradicableweaknesses, and tha t a few discussions of basic principlesof report writing frequently suffice to improve considerablythe quality and lucidity of their reports.

This pamphlet contains the essence of these discussions.Most of it is contained in some form in the existing literatureon report writing. This pamphlet is not intended, however,as a replacement for this litera ture , nor is it intended asa short summary or review course in report writing. It ispresented only as a small supplement to such formal coursesor formal directions for report preparation, and it discussesonly a few principles that experience has indicated generallyneeded special attention. In particular, it discusses basicattitudes, some elements of composition, the organization


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and conten ts of the report, and the editorial review. Stressthroughout is on striving for clarity, for if th is one ideal canbe deeply impressed upon the report writer, the desiredresult will have been largely achieved.

Since technical information is transmitted not only inwritten reports bu t also in talks and lectures, as during tech-nical meetings or formal conferences, a section has been in-cluded on the technical talk-the orally delivered technicalreport, Some special treatment of this subject was consid-ered necessary because the technical worker frequently showshimself to be profoundly unaware of the difference betweena written and an oral report. Here again the emphasis hasbeen laid on principles found frequently to need attention,and no effort has been made to provide a thorough discussionof the oral report or of public speaking.

BASK ATTITUDEPurpose

The purpose of the report is to present information.You will hardly disagree with this sta tem ent; yet many au-thors seem to subordinate this purpose and quite forget thepoor reader when preparing a report. For example, when areviewer complains that a certain word seems incorrect, theauthor may proceed to an unabridged dictionary and tri-umphantly point out the rare definition that clarifies hissentence. Obviously such an author is more interested indemonstrating his erudition than in presenting informationclearly to his harried reader; for if he had his reader in mind,he would try immediately to substitute a more commonphraseology.

This example is only one of many that could be given.Apparently the presumed purpose to present information isfrequently forgotten in the author's desire to show his ownbrilliance, to impress the boss, to impress the secretary, todemolish the rival, or to get a raise. Worthy as these ob-jectives may be, the basic objective should be to make the


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report clear and informative; furthermore, if this objectiveis attained, the secondary objectives will automatically beattained.

This basic viewpoint is fundamental. If you remembernothing else of this pamphlet, you will have retained theessence if, when writing your report, you continuously bearin mind the busy reader, who has only a limited time todevote to your report and who, in addition, may not bevery familiar with your subject.Honesty

The great scientists who established the foundations ofmodern science seldom had to admit an error, if for no otherreason than that they generally had time to correct anyinadequacies tha t became apparent. Th e high degreeof thoroughness and perfection that characterized theirwork, however, is often unattainable in many modernlaboratories. For example, a complete test program maybe run through a particular experimental facility beforea single result is available for examination; and the equip-ment may no longer be available when eventual examinationof the results shows that the crucial test was not withinthe range of variables chosen, or that some of the t es tswere spoiled, or that perhaps the whole program was notvery cleverly conceived. Thus , the hectic pace of modernresearch frequently results in studies that, although useful,have rather significant faults or weaknesses. Even purelyanalytical studies may suffer in this way, when the workeris forced to publish what he has and proceed to a moreurgent job.

Such situations are, of course, unfortunate, and areparticularly distressing to authors trained in admirationof the masters. What is more unfortunate, however, isthe fact th at these same authors may strive desperately t ohide the faults. They may spend days trying to concoctwording th at will lead the reader's attention away fromthe faults or tha t will make the faults appear less significant


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heroic remark by Julius Caesar, or it may be some impressivetechnical phrase equally inapplicable in the particularsentence.

The remedy for such apparently illogical outbreaks is toavojd secondary motives and efforts a t elegance and t o stayclose to straight scientific reporting. In general, if you findyourself struggling excessively in composing a statement,you might do well to pause and ask yourself whether theidea is necessary and, if so, whether it is actually complex orwhether you are muddling it as a result of extraneous motives.

CLEAR THOUGHTS, CLEARLY EXPRESSEDWordsOnly a few remarks are needed with regard t o choice ofwords. As has already been suggested, avoid using a rareword unless it is essential. Under no circumstances use acommon word in a rare usage, because it will mystify yourreader without even suggesting that he consult an unabridgeddictionary. Foreign words and phrases should not be used;whatever elegance or subtlety they may add to your paper isprobably lost on your reader, who will merely find the paperthat much more difficult to follow. These remarks, ofcourse, do not refer to the technical words of your branch ofscience. Be sure, however, that your technical words arenot merely the jargon of your own laboratory, because suchlanguage can be meaningless to workers a t another laboratory.

This advice is possibly contrary to the style encouragedduring your formal education, when your English instructormay have beamed if you used a phrase from Shakespeare ora bit of Latin in your themes. Now you must emphasizeclarity and easy readability, remembering that your readersare not English instructors, and save your ornamentationfor other occasions.


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SentencesOne cannot prescribe, for sentences, "do" and "don't"

rules th a t are as simple and obvious as those just presentedfor words. The basic purpose, however, to present yourmaterial as clearly as possible is still your guide; and thefollowing few suggestions, of' fairly general applicabili ty,will exemplify the approach.

The length of a sentence should generally not exceedabout 35 words, unless it is broken up (as by semicolons)into two or three distinct and logically consecutive parts.Any sentence presents the reader with the task of firstidentifying its constituent phrases, and then bearing themall in mind while their logical interrelation crystallizes.Forcing him to bear in mind and fit together more thanabout 10 phrases (each of about three words) is unnecessarilycruel. Here again your English instructor's joy a t yourability to compose grammatically correct 200-word sentencesmust be disregarded as against your present goal of simpli-fying your reader's job.

An equally important rule is that a sentence shouldgenerally contain some indication as to how it is related tothe preceding sentence or to the development of the para-graph. This indication is usually near th e beginning of thesentence. Fo r example, in th e first three sentences of thisparagraph, th e opening phrases ("An equally importan trule," "This indication," and "For example") all serve toshow relationship to what has gone before. Omitting suchtie-in wording may not essentially alter the main contentof the sentence, but it forces the reader to figure out forhimself how the sentence fits into your train of thought.In general, then, you must remember, while composing eachsentence, to indicate by appropriate wording how it isrelated to the preceding sentence. You must take yourreader by t he hand, and lead him step by step along the pa thby which you develop your topic.


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Make every effort to eliminate ambiguous phraseologyfrom your sentences. Unfortunately the English languageoffers many opportunities for ambiguity, as in the followingwell-known pitfall :

Time flies. You can't . They fly too fast.where the reader is quite confounded by the third sentenceuntil he goes back and reinterprets the first two sentences.Ask yourself as you write each word, phrase, or sentencewhether its meaning would be clear or whether i t has a chanceof being momentarily misunderstood.

Frequently a particular fact or idea must be stated morethan once in a report; for example, it may be given in theIntroduction and then also in the Tests and in the Discussion.Rather than treating it every time as brand-new material,you might introduce the repeat with a phrase such as "Ashas already been mentioned" or "Here, again, the factthat . . ."; otherwise the reader may wonder whether hismemory is playing tricks. Such introductory phrases arenot always essential, but their omission can sometimes bevery annoying.Paragraphs

The main characteristic of the clear paragraph hasalready been mentioned; namely, that the relation of eachsentence to the preceding or following one be clear, as bymeans of transition words or phrases. In addition, it maybe desirable to indicate definitely the relationship of eachparagraph to the preceding or the following one. Usuallythe relationship to preceding material is indicated in theopening sentence or sentences of the paragraph; and relation-ship to following material is indicated in the final sentenceor sentences of the paragraph. In any case, make surethat your reader is not required to proceed very far into theparagraph (say, beyond the second sentence) before thegeneral drift of the subject matter becomes apparent. Donot make him read on and on while wondering just how theparagraph fits into your report. You, as the author, are


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in a much better position than is your reader to organizeyour material; and the responsibility both for organizing itand for showing the organization rests on you.

Do not make your paragraphs too long. Just as asentence with too many phrases is difficult to grasp as aunit, so is the paragraph with too many sentences. A longparagraph should not, of course, be broken up into shorterones by arbitrary subdivision. If you find your paragraphgetting very long, either simplify the idea or break up theidea into smaller units, with a paragraph for each.

ORGANIZATION OF A TECHNICAL REPORTDifferent writers have different methods of organizing

their reports, and some seem to have no discernible methoda t all. Most of the better writers, however, appear to be inremarkably close agreement as to the general approach toorganization. This approach consists essentially of statingthe problem, describing the method of attack, developingthe results, discussing the results, and summarizing the con-clusions. You may feel that this type of organization isobvious, logical, and natural. Nevertheless, it is not uni-versally accepted. For example, many writers presentresults and conclusions near the beginning, and describe thederivation of these results in subsequent sections. Althoughsome obvious arguments exist for this latter type of organiza-tion, most readers and most of the better writers seem toprefer the former. The straightforward organization, then,is recommended here, not only because it seems basicallymore logical, but also because your reader will be morefamiliar with it and will therefore have to expend less effortin understanding your paper if it is so organized. Even ifhe is impatient for the final results and conclusions he canmerely turn to the back of your report; and he will hardlydemand that you destroy the logical sequence of yourpresentation in order to present the conclusions first.


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The following sections discuss the main parts of thereport in more detail. As already indicated, the detail willbe far from complete, since the purpose is only to throwsome light where the inexperienced author most oftenblunders. The experimental research report and theanalytical research report will be treated separately.The Experimental Research Report

The typical report of experimental research is organizedroughly as follows:

1 . Introduction 4. Results2 . Equipment 5. Discussion3. Tests 6 . Conclusions

The contents of these parts will be briefly reviewed.Introducfion-Many people have a notion that the In-

troduction serves to put the writer's best foot forward, tocharm the reader and excite his interest, or somehow toease the reader in to the subject matter; and they accordinglystruggle to produce a literary gem with which to begin thereport. Actually no gems are needed or are particularlydesirable. The Introduction may be written in a straight-forward manner along the lines indicated in the followingidealized outline :

(a) Begin by describing enough of the background toshow where or how the problem arose and how importantit is. For example:

As a result of such-and-such developments,such-and-such problems have arisen. In reference 1,such-and-such phases of the matter were studied.I'n .reference 2, certain other phases were studied.The results, however, leave the question of . . .unsettled, so th at the basic problem of . . . emains,and i t is not yet possible to design accurately. . . .The main question in your composing such an opening iswhether you actually know the background well enough towrite it accurately, with the emphasis placed correctly. Ifyou are not sure, reread the references or go to your super-


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visor (or to whatever expert is available) and ask him todiscuss the whole subject with you. In general, do whateveris necessary to give yourself sufficient background to com-pose an opening that will not confuse the reader with in-accurate or off-key statements.

It may happen that an adequate review of the back-ground, with enough detail to clarify the precise contributionof your report, would be much too long to be included in theIntroduction. In such a case, summarize it in this firstsection of the Introduction and provide a separate chapterfor the detailed background (or perhaps give th e backgrounddetail a t appropriate points throughout the paper, dependingon the nature of the material).

(b) Having indicated where the problem exists, or, ingeneral, what the background is, now state broadly what itis that you have tried to contribute by your research andalong what general lines you have worked. For example:

In an effort to obtain further insight into . . .,an experimental study was made o f . . ., with specialemphasis on. . . . The material available was con-sidered to be especially favorable for the study be-cause. . . . Furthermore, special apparatus (to besubsequently described) developed for this purposewas capable of . . ., thereby providing informationof (a previously unavailable) type. . . .(c) Your reader is now aware of what you have tried to

do and why. It is usually desirable at this point to add afinal portion to the Introduction, in which you state morespecifically what types of tests and analyses were made, theranges of variables considered, and similar infoxmation thatbroadly defines the nature and extent of your work. Thereader will thereby get an insight into the scope and thorough-ness of your research and will know what to expect in thereport.

These three sections thus constitute the typical In-troduction. Frequently the three sections are found inthree paragraphs, but such sharp separation is not essential.


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One of the sections may require two or more paragraphs,or all three sections may be contained in one paragraph.

The general applicability of the preceding formula,as well as the ease with which it can be applied, is illustratedby an experience in a report-writing class of about 20 youngresearch engineers. After receiving a brief lecture on thepreceding material, every member of the class was ableto write out, in less than an hour, an acceptable first draftof an Introduction for the report that he would eventuallybe writing on his research.

Apparatus and Tesfs-Normally, the final portions of yourIntroduction will have provided enough insight into thenature of your study so that little or no argument for yourchoice of equipment or technique is needed. You maythen simply give a straighforward description of yourequipment under Apparatus. If, however, some par-ticular ingenuity was involved, be sure that your presenta-tion makes the matter clear. The reason is not that youmust brag wherever possible, but that you must not presentsomething new with so little emphasis (as if i t were obviousor well known) that the contribution cannot be recognized.The same rule, of course, applies to any part of your paper;a reader becomes very bewildered when he cannot makeout from your discussion what is old and what is new.Sometimes different tests may have required differentpieces of equipment, or you may have developed yourapparatus as you proceeded from one test to the next.In such a case, do not hesitate to make Apparatus andTests a single heading. If the two are not so intimatelyrelated, however, a separate chapter, Tests, will generallybe preferable.

Results and Discussion-Some authors prefer, whereverpossible, to present all their experimental results (as in theform of charts or tables) first, under Results, and then todiscuss them, others prefer to discuss their results as theyare presented. Sometimes the subject matter develops insuch a way that one or the other method is obviously to be


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preferred. In any case, the nature of the decision is similarto that discussed for Apparatus and Tests and will not befurther discussed here. Although this par t of a report isnormally the most important part, adequate presentationdepends mainly on careful and logical analysis of the materialrather than on rules of report writing. The followingremarks, however, may be useful.

You will recall that in the Introduction you describedthe problem and what you hoped to accomplish or contribute.Bear this Introduction in mind while you present your data,and show by your discussion how these data shed lighton the problem or, in general, to what extent your originallystated objectives were achieved. Some authors also find ithelpful to prepare a list of the main points that were developedin the investigation (these are, essentially, the final Con-clusions of the report) and then to aim the Results andDiscussion t o bring out these points.

Organization along some such line is essential. Avoid arambling, disorganized presentation. Above all, avoid theponderous revelation of unenlightening trivia, such as "Itmay be seen by reference to figure 8 that the lift increaseswith angle of attack until the stall is reached, beyondwhich. . . . 9

Conc/usions-Your Results and Discussion will alreadyhave brought out the main contributions of your work. Ithas become standard practice, however, to gather togetherthese main contributions and enumerate them in a finalsection called Conclusions. Essentially, the Conclusionsstate concisely (seldom more than two sentences per con-clusion) what you have concluded from your research.They are the answer to "So you have done a piece of research.Well, what did you find out?" They should be written withlittle or no reference to the body of the report, as a favor tothose readers who like to go directly from the Introductionto the Conclusions in order to see how it turned out. Anadditional purpose in making them approximately self-sufficient is to minimize the possibility of a misunderstanding


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if they are quoted. (For similar reasons, incidentally,it is generally desirable t-hat figures be reasonably self-explanatory.)

Sometimes the research turns out in such a way thatenumerating sharply drawn conclusions is practically im-possible. In such cases a short discussion of the problemand what you learned and believe about it should be givenunder Conclusions. Sometimes, however, the original prob-lem, as stated in the Introduction, remains essentially un-answered (as when the experimental technique turned outto be inappropriate, or the information obtained turned outto be less useful than originally expected). A frank discus-sion of the situation, together with, possibly, suggestions forfuture research, is preferable in such cases to drawing unin-teresting or irrelevant conclusions. Such a final section isgenerally entitled Concluding Remarks.

Sometimes the technical report merely describes equip-ment or procedures, or it tabulates design data obtained bystandard methods. Neither Conclusions nor ConcludingRemarks is usually appropriate desirable for such a paper.If a closing section is desired, it might be a RbumC, in whichthe information is briefly sketched and the charts or tablescontaining the data are indicated.

Chapter heading-In the preceding discussion the chap-ter headings were assumed to be the standard ones previouslymentioned (Introduction, Apparatus and Tests, and so on).Although these headings are quite satisfactory, more specifictit les 'are preferable whenever they can be used. Thus, in-stead of Apparatus, you might use Wind Tunnel and Models (ortwo separate chapters, one entitled Wind Tunnel, the other,Models); instead of Results and Discussion, you might useDihedral Effect, Longitudinal Stability, and soon (again, thereis no objection to having several main headings to replace Re-sults and Discussion). The headings Introduction and Con-clusions (or Concluding Remarks or RbumC) are almost neverreplaced by more specific titles.


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Tables, charts, and figures-The inexperienced writertends to present his numerical results in the form of tables,usually because he has studied his results so thoroughly thathe can see the significant trends from the numbers them-selves. The reader, however, is much less familiar with theresults and may fail to see from the tables the trends thatseem so obvious to the author. In general, visual presenta-tion by means of charts or curves will put across yourpoints much more effectively. Furthermore you should giveconsiderable thought to the question of how to plot yourresults so that their message will be most easily grasped.Crowding too many curves on one figure should be avoidedso that the reader can easily identify each curve as youdiscuss it in the text.

State clearly in the text what each figure shows and howthe figure shows it . Avoid referring to a figure in so casuala manner (as by the simple parenthesis (fig. 2)) that thereader himself must determine how the figure is related toyour discussion.

Summary--Among the scientific journals there are anumber, such as Science Abstracts, Chemical Abstracts, andApplied Mechanics Reviews, that provide abstracts, orsummaries, of practically all published papers in their fields.The actual preparation of the abstracts is performed free,or for only nominal payment, by a large number of dedicatedscientists who do this essential work a t considerable personalsacrifice. The Summary th at you append to your paper isyour contribution to this effort, and it should be preparedin such a way as to lighten the abstractor's burden. Thatis, it should be capable of being used directly as the abstractor of being easily summarized further if a relatively shortabstract is desired.

In general, the Summary should contain only a minimumof background and should proceed as quickly as possible todescribe what was learned. Considering that the reportitself may not be readily accessible to the reader, put into


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the Summary what you consider to be the most valuablecontributions that the report makes, including the mostsignificant conclusions and some mention of interestingtechniques or concepts. There is no room, of course, for allthe detail that you would like. In any case, however,include enough so that the reader can determine whetherhe should exert himself to get a copy of the report itself forcloser study.

Note that the Summary is not actually a part of thereport itself, so that duplication of portions of the reportneed not be avoided. For example, you need not hesitateto include sentences lifted unchanged out of the Introduction,Conclusions, or any other part of the report.

The reader of a report will frequently begin by readingthe Summary in order to get a quick review of the contents.You need not give any extra thought to such a reader, how-ever, since the material tha t satisfies the primary purpose ofthe Summary will adequatelyderve this additional purposealso.The Analytical Research Report

Theoretical or analytical papers may not fit into stand-ard organizational patterns as readily as do the usualexperimental papers. The remarks previously made withregard to the Introduction and Conclusions still apply, butthe body of the paper is arranged in whatever mannerseems most logical. A long theoretical development, how-ever, frequently tends to leave the reader unable to see thewoods for the trees. Accordingly, you might do well toinclude near the beginning of such a report an overall viewof your line of development, and as you begin each chapter,indicate what will be done in that chapter and how it fitsinto the development. Incidental material, such as a sideproof or derivation, may be put into an appendix in order toavoid interrupting the continuity of the main development.


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RE V I EWS AND CRIT ICISMSAfter your paper has been completed, it will generally

be reviewed by one or more separate reviewers or by a re-viewing committee. Ma ny authors seem t o consider sucha review to be an unwarranted impertinence, and theyapproach the review with various bewildering psychologicaldefenses, ranging from "Here I am. Crucify me!" t o "Doyou wanna fight?" Needless to say, such atti tudes are absurd.Your purpose should not be to exhibit your own brillianceas against the reviewer's wickedness and stupidity, but onlyto make your paper more readable and more accuratescientifically.

Consider all comments and suggestions carefully. Someof them may be incorrect or may indicate that the reviewerhas not understood you. In such cases, do not scold thereviewer, but try to determine where he was misled andconsider whether others might be similarly misled. If anappreciable likelihood exists, try to revise the material sothat this danger will be minimized. Remember at all timesthat your report should be clear and that your reviewer isprobably a typica l reader-or is at least typical of a consider-able proportion of your readers. The fact tha t you canexplain a passage to his satisfaction does not mean that thepassage is satisfactory; it must be written so tha t i t will beclear to the reader even when you are not present to explainit.

Sometimes the reviewer will make an important tech-nical contribution to your report, such as a clearly superiormethod of developing an equation. Such contributionsshould be accepted. Do not insist on publishing inferiormaterial merely because you do not wish to take credit forwhat is not yours. Your responsibility to your reader isstill paramount. It may be appropriate, however, toacknowledge the reviewer's contribution in the text, to askhim to write an appendix under his own name, or to makehim a coauthor.


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THE TECHNICAL TALKYou have doubtless been subjected to the lecturer who

buries his face in his papers and, in an expressionless voice,reads long involved sentences while waving vaguely towardhopelessly complicated charts. One may wonder why anyrational person would commit such an atrocity; yet manyresearch workers actually seem to have no better conceptof what a technical talk should be. Needless to say, thetalk, like the printed report , should convey information.Simplicity

You will be given, say, 20 minutes in which to presentto visiting scientists a review of your research. Your firstreaction is to insist that you need more than 20 minutes.Your arguments will be rejected, however, so you eventuallyproceed complainingly to your task. With great ingenuityyou apply yourself to outwit your stubborn and arbitraryboss by getting an hour's material into a 20-minute talk.You concoct long and brilliantly comprehensive sentencesfor your discussion, you organize all of your numericalresults so that you can present them in rapid-fire order, andyou lay out 15 slides, each crammed with detailed informa-tion. Unfortunately, when you first read through yourprepared speech, it takes nearly 30 minutes instead of 20.You are not very disturbed, however, because you areconfident that, with a little practice, you will be able toincrease your speaking rate until the delivery time is downto the required 20 minutes.

All that is missing from your approach is considerationfor the central figure-the man in the audience. After2 minutes of your talk he will be rapidly developing mentalindigestion; after 5 minutes he will have lost the thread ofyour discussion; and during the remainder of your talk hewill simply concentrate on hating you or on trying to sleep.If you will consider that he will probably hear about 15 talksduring the day, on a variety of subjects in perhaps none of


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which he is expert, and if you will ask yourself how much aperson can hope to learn in one day (learn, th a t is, so th a t hewill remember it for a long time), you will see the futility oftrying to cram detailed information into him as if you werestuffing a goose. Actually, your mission will usually besuccessfully accomplished if you leave him with a fairlyclear impression of the nature of your work and of yourmost significant results or contributions.

In preparing your talk, then, your first task does notconsist of gathering together all of your data so that not asingle detail is missing, but rather in thinking over yoursubject and deciding just what fundamental progress youhave made, or what new fundamental ideas you have devel-oped, that you wish to give your hearer to carry away withhim. In fact, you will do better not t o reacquaint yourselfwith the details at this time, because if you yourself haveforgotten them they certainly do not represent the basic newideas or contributions that you would like your hearer toremember. Details such as numerical da ta have their place,of course, in the technical ta lk ; but you must make clearwhether the numbers are of such fundamental importancethat they should be remembered as such, whether they arepresented for comparison with other numbers, as in showingtrends or in showing agreement between theory and experi-ment , or whether they are presented merely to show thethoroughness or the scope of your work (as when theresearch consists of determining large quantitities of designdata).

You should next consider how to organize your pre-senta tion with utmost simplicity and logic, so as to maximizethe probability that your hearer will absorb your story.As to whether the allotted time is adequate, the questionneed not concern you. You should be able to describe yourwork in any specified amount of time, be it 1 minute or1 hour, and all tha t is required of you is tha t you present asinformative and understandable a story as possible withinthe allotted time.


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Choice of Language and Gen eral Approa ch to PresentationSuppose that your friend Joe should ask you to tell

him about your research. Would you proceed with languageof the following type?

The momentum method of measuring profiledrag, which consists of making total-pressure andstatic-pressure measurements across the wake andinserting these measurements into certain integralexpressions developed by Betz and Jones, has beenan important addition to experimental aerodynamics.Unfortunately, application to flight evaluation of thedrag contributed by wing surface roughness or byvarious protuberances has been hampered by theexperimental difficulty of making the necessarynumber of simultaneous pressure measurements inthe wake.In the present research, an effort has been madeto reduce fhe experimental complication in orderthat application to flight testing may be made morepractical. . . .Such sentences might well be the introductory sentences

of a printed technical report; but as spoken material theydemand a degree of concentration that most listeners cannotmaintain. If, in addition, they are spoken in a rapid mono-tone, the listener's position is hopeless almost from the verybeginning.

Actually, as a result of your years of experience inconversation, both technical and nontechnical, you havedeveloped a speaking style that is not too demanding ofeither your own or your listener's mental processes, and thatserves satisfactorily to convey your ideas; and this speakingstyle, in general, is entirely different from that of a printedtechnical report. Using this style, you would speak to Joeperhaps as follows:

You're probably familiar with the momentummethod of measuring profile drag (a pause, whileyou look at him to see whether he nods his head ormerely looks blank; you decide to add a few words of


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explanation), in which you measure total and staticpressures at a number of points across the wake,put the readings into certain formulas, and finallyintegrate across the wake to get the drag (a pause)-the profile drag, that is. The method ought to beespecially useful for flight measurements behindactual airplane wings, in order to determine the dragdue to (a pause, a slight motion of the hand, whileyou think of examples) rivet heads, gun ports, orany other irregularities. Now, trying to make all thosemeasurements in the wake would require rathercomplicated instrumentation-which is the reasonthat it hasn't been done-and what I have tried todo is to simplify the method-especially to simplifyth e instrumentation-down to something morepractical. . . .Such language and the indicated mannerisms (pauses,hand motions, and so on) are more characteristic of some

people than of others. Your own normal manner of speak-ing, for example, may be entirely different. There is noobjection a t all to your having and expressing your ownpersonality; and it is definitely not suggested that you tryto imitate anyone else's mannerisms or style of speech.The point emphasized here is th at , in general, merely readingor reciting a carefully written technical report does not con-st itute a technical talk. In your daily technical discussionswith your coworkers, or if you were teaching a class, youwould not expect your friends or students to understand youif you poured forth such formal language-especially if youspoke rapidly and with an expressionless voice; and youshould not demand more of an audience a t a technicalconference.

The conclusion, then, is that the technical talk is notmerely a technical report that is short enough to read orrecite in, say, 20 minutes; rather, i t is a monologue, presentedin whatever conversational, or perhaps teaching, manneris natural to you, in which you try your very best to getacross a few basic ideas to your audience. Since the manin your audience cannot reexamine any sentence or para-


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graph th at he finds confusing, you must make every thoughtclear enough to be understood the first time. If the thoughtis a difficult one, you may even find it best to repeat it.You may repeat it in the identical words, or you may usedifferent words and a slightly different approach. Forexample, add "Perhaps you didn't quite follow that idea.What I mean is that if . . . ." Speak easily and not toorapidly. Even an awkward hesitation, while you grope forthe right word (just as in normal conversation), may havesome value in t hat i t excites the hearer's interest whilehe tries sympathetically to guess the word you want. Avoid,however, affecting excessive casualness or extemporaneous-ness, since the effectiveness of the talk can be spoiled bythe appearance of carelessness in its preparation or lackof earnestness in its presentation.In general, the talk should not be written out duringits preparation. The inexperienced speaker will usually beunable to write anything but the formal sentences of thetypical printed report, so that his talk is ruined from themoment he puts pencil to paper. Compose it entirely inyour mind, and, as you compose each sentence, make thehand motions, hesitations, facial expressions, and so on thatwill accompany it. At the same time ask yourself whetherit will be clear; and if not sure, struggle with it some more.After you are satisfied with your opening sentences, yourconclusions, and a few other especially critical sentences,you may write them down in order to assure having themexactly as you composed them. Do not try to improvethem as you write them down, however, for you will surelyspoil them.

The question as to whether your talk should be memo-rized will now be seen as rather irrelevant and misleading.After you have composed and rehearsed your talk so thatin two successive rehearsals (alone or with a friend) youwere satisfied with it, you may be sure that the final talkwill be satisfactory. Some speakers will, by th is time,


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have essentially memorized every word and gesture, whileothers will remain quite flexible as to detail. There isactually very little chance that you will forget anythingimportant, and no more than a small card outlining yourmain points should be taken with you t o the speaker'sstand.It is not intended here to imply that preparing anddelivering a talk in this manner is a simple task for theinexperienced. The same, perhaps, applies t o almost allthe precepts presented in th is pamphlet-they are easierto agree with tha n to incorporate in your style. On theother hand, the task is not nearly so formidable as manypeople seem to believe. The technique is merely onemore of those that could not be taught in your formalschooling bu t th a t you have t o learn in order t o be effectivein your job.

Does the danger of stage fright make you want to relyon writ ten copy? Actually, much less reason exists foremotional reactions in technical talks than in typical college"public speaking." In the lat ter , emphasis is generally ondemonstrating or exhibiting the speaker, with the contentsof his speech of minor significance, whereas, in the technicaltalk, the contents are of param ount importance, whilethe speaker is merely the medium through which they arepresented. If you should ever listen to the comments ofan audience after a technical conference has adjourned, youwould find that oddities of presentation, such as strangeaccents, speech defects, nervousness, or even grotesqueeccentricities of manner seem to go virtually unnoticed solong as they do not interfere with intelligibility, while bittercriticism is applied to speakers who read incomprehensiblepapers. Bear in mind, then, th at you are no t required togive a polished performance, bu t only a clear one. Yourlisteners are not interested in judging you. They want onlyto understand what you are telling them.


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Visual AidsI n the preceding discussion the point has been emphasized

repeatedly that your technical talk should resemble as closelyas possible the description of your work that you might giveto your friend Joe. Just as you might show him your appara-tus or your plots, or perhaps go to the blackboard and makean explanatory sketch, so should you use the same or similarvisual aids in your talk . Instead of being shown on paperor on the blackboard, your illustrative material will normallybe on charts or slides, prepared in advance with all necessaryaccuracy, clarity, and neatness. Do not consider, however,th at such previous preparation saves much time in the pres-entation, or that you may present a chart with nothing morethan a vague gesture and a remark like "This chart illustrateswhat I have just said."Actually, your charts and slides form the backbone ofyour talk, and each must be presented with utmost effort a tclarity. State the subject of the slide, say what the abscissasand ordinates are, explain, if necessary, the special signifi-cance of these abscissas and ordinates and of the method ofplotting, and, if th e origin is not a t the juncture of the scales,mention that fact also. Run your pointer along each curveas you describe it, and tap sharply with your pointer a t anypoint on the curve to which you call special attention. (Butavoid vigorously rubbing or gouging the projection screenwith th e pointer, as the glass-bead surface is easily damaged.)Furthermore, the language used while discussing your slidesshould be appropriate to your use of the pointer. Forexample, say "This top curve shows . . ." rather than "Theupper curve of figure 5 shows . . ." or "You can see in thisequation that this term cancels this term and this termcancels this term" rather than "It may be seen in equation (4)th at the third and fourth terms on the left side are canceledby the second and fourth terms, respectively, on the rightside."


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Technical talks frequently seem to be organized aroundslides or other visual material. The talks seem to consistonly of descriptions and discussions of the slides, and eventhe Introduction and the Conclusions may depend on slides.There is no objection to such a presentation, so long as thespeaker gets his message across. You must not concludefrom such talks, however, that the slides were preparedfirst and the talk was then composed around them. Slidesand charts should be composed along with the talk, notbefore it. Avoid preparing them first and then trying todecide what to say about them, because a considerable lossof smoothness and logic may result.The Printed Versi0.n

If a printed version of your talk is to be included inpublished proceedings of the meeting, write it in the moreformal style of printed reports; but by no means feel obligedto carry over the same language and coverage into the talkitself. The printed version may, indeed, include data anddiscussion that had to be omitted from the talk, and mayeven include figures and tables that were not - used in thetalk itself. Such extensions of the paper should be heldwithin bounds, however; published proceedings of technicalmeetings are not usually intended as substitutes for normalpublished reports.

25U. S. GOVERNMENT PRINTING OFFICE : 1968 0 - 314 - 680


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"T he nerot~ 'iuticul cni i spcre i rr t i z i~ ieso f t he Ul l i fed States . fhd! / beco~j i i i tc fed o ns to co?ztr.ibz~te . . t o he e s p n i l j i o i ~ f hrlnzn~i~ ) I O L L ~ -edge of phe?zornt.iin it2 the utmoiphct.e i ~ i ~ dp nc e. T h e i l d ~ ~ j ~ z i . r t i . n t i o ? ~s h d l provide for the z~; idest t~act icabieG I I ~ ppr.op~,i,itr iisscnzj~intjoizof i12f ormctioiz co~zcet~iz i~zgit^ a ~ t i zties ntzd the r e ~ n i t jher,t-'o .

NASA SCIENTIFIC AND TECHNI CAL PUBLI CATI ONSTECHNICAL REPORTS: Scientific and technical information consideredimportant, complete, and a lasting contribution to existing knowledge.TECHNICAL NOTES: Information less broad in scope but neverthelessof importance as a contribution to existing knowledge.TECHNICAL MEMORANDUMS: Information receiving limited distri-bution because of preliminary data, security classification, or other reasons .CONTRACTOR REPORTS: Technical information generated in con-nection with a NASA contract o r grant and released under NASA auspices.TECHNICAL TRANSLATIONS: Informa tion published in a foreignlanguage considered t o merit NASA distribution in English.TECHNICAL REPR INTS: Information derived from NASA activitiesan d initially published in th e form of journal articles.

SPECIAL PUBLICATIONS: Information derived from or of value toNASA activities but not necessarily reporting the results of individualNASA-programmed scientific efforts. Publications include conferenceproceedings, monographs, data compilations, handbooks, sourcebooks,and special bibliographies.

Deta i ls on the ava i la b i l i ty o f these publications ma y be obta ine d f rom:

SCIENTIFIC AND TECHNICAL INFORMATION DIVISIONNATIONAL AERONAUTICS AND SPACE ADMINISTRATION

Washington, D.C. 20546

Clarity in Technical Reporting

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