COUNTER HEIGHT AND FINGERPRINT SCANNER ANGLEA case study on the importance of experimental rigor

Mary Theofanos

Brian Stanton

Human Computer Interaction2 Views of the Same System

2

System starts capture

Capture

Capture thresholding

Time

Engineering

Capture repeated if unacceptable

Human Factors

Participant presentsAttempt starts

Next attempt(acceptable

attempt)

Attempt

Attempt ends

Why is experimental rigor so important in our program?

Test must be valid That we are really testing what we say

we are Results must be repeatable

Everything documented so someone else can replicate

Results must be generalizable We usually can’t test everyone so we

want to test a sample and generalize to a larger population

Our results are fielded quickly

Why is rigorous design necessary?

Think of it as taking noise out of the system

Experimental Design

Introduction Method

Participants Equipment Procedure

Results

What question does this study try to answer?

Introduction

Problem:

United States Visitor and Immigrant Status Indicator Technology (US-VISIT) transitioning to a 10-print process (new scanner)

Existing counters too tall for a 10 print Can’t change the existing counter heights ($)

US-VISIT needs: Throughput – process travelers as quickly as

possible Quality – collect best possible fingerprint

images Customer Service – concerned for travelers

comfort and safety

How about angling the scanner?

Given current surface heights, what is the “best” angle for a electronic fingerprint scanner?

Question:heights “best” angle

Heights

30 33 35 36 37.5

38 39 43 45 47 48 490

102030405060708090

100

Border Entry Counter Heights

Counter Height

Fre

qu

en

cy

Heights

Scanner Model at three heights 39” 45” Practical

Midpoint 49”

39”45”

49”

Angles

With CAD Software looked at a Range of Angles at the three Heights Example: 39”

Angles

Selected Range of Angles0°10 °20 °30 °

0° 10° 20° 30°

3 Heights and 4 Angles

Heights 39” 45” 49

Angels 0° 10 ° 20 ° 30 °

What to collect and how to collect it?

Method

Who does this study address?

The flying publicRepresentative of

What characteristics of the traveling public are important?

AgeHeightGenderAbility

Age

People between the ages of 14 – 79 are required to present prints when arriving in the US.

Height

Population Height

5th Percentile Female149.9 cm (59.0 in)

95th Percentile Male184.9 cm. (72.8 in.)50th Percentile

166.6 cm (65.6 in)

Gender

Equal mix male and female

Ability

Assumption: disabled travelers will have an alternative method.

Participants

Representative of the traveling public 14 -79 Years Even numbers of men and women Heights ranging from 150 cm. to 185 cm.

Participants’ Rights

Institutional Review Board…to review the ethical acceptability of all research conducted where human subjects are used…

To protect the physical and psychological well-being

of subjects

To serve as a safeguard to protect against errors in

ethical judgment

To assure human subject testing is in compliance

with Part 27 of Title 15 of the Code of Federal

Regulations

To protect the privacy of the participants

Scanners

Equipment

Two Electronic Fingerprint Scanners

Each was compliant with Department of Homeland Security’s requirements and was supplied to us. Capable of taking a 10 print 6” x 6” x 6”

Table

Equipment

Adjustable Table

Equipment

Scanner Angle

Equipment

Scanner Angle

Equipment

Now we know the heights and angles and all the equipment, how do we put them together?

Experimental Design

Between Variables and Within Variables

Between: Each participant is tested on one condition

Within: Each participant is tested on every condition (repeated measures)

It takes some analysis to know when and how to use them.

Between Participant Design

39” 0°

39”

10°

39”

20°

39”

30°

45” 0°

45”

10°

45”

20°

45”

30°

49” 0°

49”

10°

49”

20°

49”

30°

Height Angle

Within Participant Design

39” 0°

39”

10°

39”

20°

39”

30°

45” 0°

45”

10°

45”

20°

45”

30°

49” 0°

49”

10°

49”

20°

49”

30°

Height Angle

Mixed Design

Height Angle

Angle Angle AngleAngle

HeightAngle Angle AngleAngle

HeightAngle Angle AngleAngle

Experimental Design

4 Angles 3 Heights

3 x 4 mixed design

12 possible combinations

Each person gets a height and each angle

0° 10° 20° 30°

0° 10° 20° 30°

0° 10° 20° 30°

39”

45”

49”

Experimental Design

Since each person gets every angle, order of presentation was counterbalanced

Right/Left start Randomly Selected

0° 10° 20° 30°

0° 10° 20° 30°

0°

Right

Left

10°

Left

Right

20°

Right

Left

30°

Left

Right

39”

45”

49”

What do you collect and how?

Data Collection

What to measure?

Given current surface heights, what is the “best” angle?

Definition: ISO 13407:1999 “Usability: The extent to which a product can be

used by specified users to achieve specified goals with effectiveness, efficiency, and satisfaction in a specified context of use.”

What to measure?

Given current surface heights, what is the “best” angle?

Best = US-VISIT needs:

process travelers as quickly as possible Efficiency – : Timing – Time to complete task

collect best possible fingerprint images Effectiveness – : Quality – How good were the

prints concerned for travelers’ comfort and safety

Satisfaction –: Comfort - Questionnaire

effectivenessefficiency satisfaction

Timing

Opportunity (“please place your hand on the scanner”)

System starts capture

Capture

System ends capture (“Please remove hand from scanner”)

Capture thresholding

Time

System

Participant presentsAttempt starts

Attempt

Attempt ends

Next attempt(acceptable

attempt)

Participant

Data: How many participants?

12 prints/angle

Data

12 prints/angle

× 4 angles = 48 prints/height

Height0°

Right SequenceIndex

Middle

Ring

Little

Right Thumb

Left SequenceIndex

Middle

Ring

Little

Left Thumb

ThumbsRight Thumb

Left Thumb

10°Right Sequence

Index

Middle

Ring

Little

Right Thumb

Left SequenceIndex

Middle

Ring

Little

Left Thumb

ThumbsRight Thumb

Left Thumb

20°Right Sequence

Index

Middle

Ring

Little

Right Thumb

Left SequenceIndex

Middle

Ring

Little

Left Thumb

ThumbsRight Thumb

Left Thumb

30°Right Sequence

Index

Middle

Ring

Little

Right Thumb

Left SequenceIndex

Middle

Ring

Little

Left Thumb

ThumbsRight Thumb

Left Thumb

DataHeight

0°Right Sequence

Index

Middle

Ring

Little

Right Thumb

Left SequenceIndex

Middle

Ring

Little

Left Thumb

ThumbsRight Thumb

Left Thumb

10°Right Sequence

Index

Middle

Ring

Little

Right Thumb

Left SequenceIndex

Middle

Ring

Little

Left Thumb

ThumbsRight Thumb

Left Thumb

20°Right Sequence

Index

Middle

Ring

Little

Right Thumb

Left SequenceIndex

Middle

Ring

Little

Left Thumb

ThumbsRight Thumb

Left Thumb

30°Right Sequence

Index

Middle

Ring

Little

Right Thumb

Left SequenceIndex

Middle

Ring

Little

Left Thumb

ThumbsRight Thumb

Left Thumb

Height0°

Right SequenceIndex

Middle

Ring

Little

Right Thumb

Left SequenceIndex

Middle

Ring

Little

Left Thumb

ThumbsRight Thumb

Left Thumb

10°Right Sequence

Index

Middle

Ring

Little

Right Thumb

Left SequenceIndex

Middle

Ring

Little

Left Thumb

ThumbsRight Thumb

Left Thumb

20°Right Sequence

Index

Middle

Ring

Little

Right Thumb

Left SequenceIndex

Middle

Ring

Little

Left Thumb

ThumbsRight Thumb

Left Thumb

30°Right Sequence

Index

Middle

Ring

Little

Right Thumb

Left SequenceIndex

Middle

Ring

Little

Left Thumb

ThumbsRight Thumb

Left Thumb

Height0°

Right SequenceIndex

Middle

Ring

Little

Right Thumb

Left SequenceIndex

Middle

Ring

Little

Left Thumb

ThumbsRight Thumb

Left Thumb

10°Right Sequence

Index

Middle

Ring

Little

Right Thumb

Left SequenceIndex

Middle

Ring

Little

Left Thumb

ThumbsRight Thumb

Left Thumb

20°Right Sequence

Index

Middle

Ring

Little

Right Thumb

Left SequenceIndex

Middle

Ring

Little

Left Thumb

ThumbsRight Thumb

Left Thumb

30°Right Sequence

Index

Middle

Ring

Little

Right Thumb

Left SequenceIndex

Middle

Ring

Little

Left Thumb

ThumbsRight Thumb

Left Thumb

× 4 angles = 48 prints/height

12 prints/angle

× 20 people (120 people total) = 960 prints per height

× 3 heights = 2,880 prints/scanner

× 2 scanners = 5,760 total prints

Demographics

Age  Gender Handednes

s Right

Handed Left Handed

Ambidextrous

Height

Questionnaire

Which angle did you find most comfortable? 0 degrees 10 degrees 20 degrees 30 degrees

 Which angle did you find least comfortable? 0 degrees 10 degrees 20 degrees 30 degrees

 Please rank the following angles in order of preference by writing a 1, 2, 3 or 4 next to each angle. 1 is most preferred, 4 is least preferred.   0 degrees 10 degrees 20 degrees 30 degree

Detailed Protocol and Procedures Two teams

Two identical collection platforms Backups for each system and device Run throughs and dry runs Formal schedules Test scripts Explicit instructions and procedures Observation forms Completed the testing (120 participants in

2 weeks)

Above all be humble in the face of the data

Results

Efficiency: Task Time

Task Angle

Table Heigh

t

Participant

Height

Median Time

(s)

1 right slap

- - - 10.03

2 right thumb

- - - 10.53

3 left slap - - - 10.00

4 left thumb

- - - 10.01

5 both thumbs

- - - 10.03Task Angle

Table Heigh

t

Participant

Height

Median

Time (s)

1 right slap

- - + 16.83

2 right thumb

- - - 16.81

3 left slap - - + 16.87

4 left thumb

- + - 16.85

5 both thumbs

- - + 11.38

Scanner A

Scanner B

Significance for Time ("+" : p<0.05)

For each response variable of time we examined the factors of angle, table height, and participant height

We found: No significant effect due to angle on the time required to complete fingerprint task

Effectiveness: Fingerprint Quality Determining Fingerprint Quality of a slap

is controversial Performed the analysis 3 ways for

completeness No significant effect on Quality due to

Angle

User Satisfaction

Taller participants indicated that the 30° angle was least comfortable.

Shorter participants indicated that the flat angle was the least comfortable

Observational Data

Participant Performance Scanner Performance

DHS implementation based on our findings

Scanner in action

Our findings have implications

Start with right hand Use single thumb

Thumb rotation Grasping scanner

Angle scanner One scanner performed

better

Start with right hand Use single thumb Angle scanner Selected better

performing scanner

Our Experimental Findings

US-VISIT Field Recommendations

Thank you

100 Bureau Dr.Stop 8940Gaithersburg MD 20899

http://fingerprint.nist.gov/ Biometric Usability NISTIR 7504, Usability

Testing of Height and Angles of Ten-Print Fingerprint Capture

maryt@nist.gov brian.stanton@nist.gov