Scientific WritingScientific Writing

MEST 201MEST 201

Pr.Dr.Ramez BedwaniPr.Dr.Ramez Bedwani

OutcomesOutcomes::

•By the end of this lecture, the student will be able to Know definition, uses and types of statistics.

Material And Methods

Patients And Methods

Material and Methods, WhyMaterial and Methods, Why??

Details that can help any researcher to follow the same steps.

Assure generalizability.

Assure avoidance of different types of bias.

•New methods are described in details.

•Previously published methods:

Common:Enumeration+ref.

-Uncommon: Short summary + ref.

Title page

Abstract

Introduction

Materials & Method

Results

Discussion

Summary

References

Tables

Figures

Legends to Figures

Materials And MethodsMaterials And Methods

General AdviceGeneral Advice

Which tense to use in the Methods Which tense to use in the Methods sectionsection

•Use past tense throughout:–“We recruited 143 patients with moderate

persistent asthma”.…

Material and Methods, What?

1. Research Design.2. Setting.3. Selection of Study Population. 4. Sample size calculation.5. Data collection and Operational definition of variables.6. Procedures.7. Materials.8. Statistical methods.9. Ethics.

Material and Methods, What?1-Research Design

Research Design:

plan chosen to answer the research Q.

Research Objective VS Research Design

Estimation ------ Cross Sectional Study

Association ---- Case Control Study

Cause Effect Relation -- Cohort Study

Evaluation of Intervention- Clinical Trial

Research Design StatementResearch Design StatementExampleExample

Research Design :

Cross sectional study

Case Control Study

Cohort Study

Double Blind Randomized Clinical Trial

Material and Methods, What? 2- Setting

Setting

e.g. Out patient, Hospitalized patients, Cases in ICU

Health units in rural areas, ……..

Setting Statement Setting Statement ExampleExample

Study Setting:

The study was conducted in a semi rural area located about 25 miles from the city Karachi, Pakistan”

“Maternal Charctersitics in relation to income in”..………

Eastern Mediterranean Health Journal, 13, 6, 2007

Material and Methods, What?3-Study population

Sampling method Inclusion and exclusion criteria Method of allocation of groups

Population and SamplingPopulation and Sampling

•Population: what was the source of the population studied?

•Dates of Data Collection: give the period over which data were collected.

Population and SamplingPopulation and Sampling

•Selection: How were individuals selected into the study?

Inclusion criteria

Exclusion criteria

Clinical and pharmacological variables as a risk factor Clinical and pharmacological variables as a risk factor forfor

nifedipine-induced gingival overgrowthnifedipine-induced gingival overgrowth

Eighteen patients taking nifedipine in regular doses for at least six months ( EXPOURE) participated in the study between 2003–2005. Prior approval was received from the Ethics Committee. Patients enrolled in this study were obtained from outpatients attending the Cardiology Department at the Faculty of Medicine,Hacettepe University ( SETTING).

Australian Dental Journal 2007;52:(4):295-299

Clinical and pharmacological variables as a risk factor Clinical and pharmacological variables as a risk factor forfor

nifedipine-induced gingival overgrowthnifedipine-induced gingival overgrowth

Only patients who possessed at least 12 anterior teeth in both upper and lower arches participated in the study. Mean daily nifedipine dose was 30 mg in all patients.

Exclusion criteria were:smoking, periodontal treatment undertaken less thansix months prior to the baseline visit, concomitantsystemic disorders known to affect the periodontaltissues, and use of phenytoin and cyclosporine. Patientswith periodontitis (both treated and untreated) werealso excluded from the study

Australian Dental Journal 2007;52:(4):295-299

Material and Methods, What?4.Sample size calculation.

Sample Size is critical to precision of the estimate and power of the study.

Factors Affection Sample Size Factors Affection Sample Size CalculationCalculation

Confidence level (1- )

Power (1- )

SD

Sample Accuracy

Sample Size StatementSample Size StatementExampleExample

•Sample size required is 30 to achieve 80% power at 5% level of significance, provided that prevalence of the outcome is …% and

maximum error in estimate equal to% … .

•Reference:

•The sample size was calculated using NCSS 2004 and

PASS 2000 Program.

Sample Size StatementSample Size StatementExampleExample

..…to detect a mean difference of at least 10 mm Hg The minimum sample size required in each group is 52 to achieve a study power of 80%

and level of confidence 95% .

•References:

The sample size was calculated using Medcalc Program version 8.1NCSS 2004 and PASS 2000 Program.

5 .Data collection and Operational definition of variables

Operational definition of outcome variables and independent variables.

Main variablesMain variables

•Outcome variables :–Dependent variables

–In observational studies: what you are trying to predict

–In Clinical trials: endpoints: Primary

Secondary

Main variablesMain variables

Exposure VariablesMain exposures of interest

Confounders/Effect modifiers

Main VariablesMain Variables

Operational definition of variables

Transformation of variables

Creation of categorical variablesWhy?

Number of levels?

Predefined levels or quantiles?

MeasurementsMeasurements

Who made the measurements?

What qualification did they have for the

job ?What training was undertaken?

Were they and/or the patients masked (blinded)?

MeasurementsMeasurements

•Conditions of measurement–Sitting, standing,… after 10 minutes rest… ,

•Instrumentation–Including model, source and supplier of

instruments

•Precision of measurements

•Source of consumables

Data Collection and definition of VariablesData Collection and definition of Variables

e.g. BMJ. 2006 March 4; 332(7540): 521–525 .

•Chronic stress at work and the metabolic syndrome: prospective study

Data on the components of the metabolic syndrome were collected during the clinical examination, using the definition of the National Cholesterol Education Program by the presence of three or more risk factors( Ref).

We used obesity (defined as body mass index > 30) as an indicator of risk for the syndrome .

Data Collection and definition of Data Collection and definition of VariablesVariables

e.g. BMJ. 2006 March 4; 332(7540): 521–525 .

Chronic stress at work and the metabolic syndrome: prospective studyData collection and definition of Variables:

Data on the components of the metabolic syndrome were collected during the clinical examination, using the definition of the National Cholesterol Education Program by the presence of three or more risk factors( Ref).

We used obesity (defined as body mass index > 30) as an

indicator of risk for the syndrome .

Clinical and pharmacological variables as a risk factor Clinical and pharmacological variables as a risk factor forfor

nifedipine-induced gingival overgrowthnifedipine-induced gingival overgrowth

definition of Variables

Gingival overgrowth was assessed in both verticaland horizontal dimensions at each papilla on the buccaland lingual aspects. A total of 20 dental papilla

)10 maxillary papilla and 10 mandibular papilla (wereevaluated in each patient in the anterior region. Theheight of the gingival tissue was measured from thecemento-enamel junction (CEJ) to the free gingivalmargin according to Miller and Damm’s index (0, 1, 2,

3 scores).16

Australian Dental Journal 2007;52:(4):295-299

5 .Data collection and Operational definition of variables: Measurement

. Measurement

(validity, reliability, precision)

5 .Data collection and Operational definition of variables

• 8. Material e.g. Identify precisely all drugs and

chemicals used including: generic names, doses and routes of administration.

66 . .ProceduresProcedures

•Describe:

• Surgical technique .

• -Radiological technique .

• -

MaterialMaterial

•If drug (preparation, dose, timing…etc).

8- Statistical methods.

– Describe in details

Assumptions for Statistical AnalysesAssumptions for Statistical Analyses

Independence, normal distribution, multiple measurements.…… ,

Statistical analysisMann Whitney U-test test was used to compare data in responders and non-responders. For correlations between GCF–plasma drug concentrations, clinical parameters and demographic parameters, Spearman’s correlation rank was used. Fischer’s exact test was also used to determine the difference between males and females.

Statistical methods StatementStatistical methods StatementExampleExample

Statistical Analysis

We used logistic regression analysis to assess the odds ratios of the metabolic syndrome for the different explanatory variables

•BMJ. 2006 March 4; 332(7540): 521–525 .•Chronic stress at work and the metabolic syndrome: prospective

study

A few words about mathA few words about math……

•Equations are often necessary to describe in the methods

•Peripheral equations should be avoided or moved to an Appendix –

•Define all terms in your equations.

Statistical AnalysisStatistical Analysis

•What comparisons were made?–In trials was the comparison by “intention to

treat” or “per protocol?”

•Using what technique?

•What software was used and (where relevant) which programs?

•)What p-values were taken to be significant(

Statistical AnalysisStatistical Analysis

•Justify any sub-group analyses:–Were they in the original protocol?

–Why were they done?–Were they post-hoc, because you didn’t find

what you originally expected?

Ethical permission must be

acknowledged in the methods

section.

Title page

Abstract

Introduction

Materials & Method

Results

Discussion

Summary

References

Tables

Figures

Legends to Figures

99 - -EthicsEthics

Evaluation of the Evaluation of the

Materials and MethodsMaterials and Methods

The reviewer asks the following questions:

1 -Is the study population detailed

adequately?

2 -Are the methods described well enough to

reproduce the experiment?

3 -Is the study design clear?

4 -Are statistical methods included?

Title page

Abstract

Introduction

Materials & Method

Results

Discussion

Summary

References

Tables

Figures

Legends to Figures

AssignmentAssignmentTopicStudent Names

Types Statistical Analysis

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