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Nathan Thompson, PhD
Terry Ausman
Statistical Detection: Where do I start?
Welcome!
 This is some of the lessons I have learned
while diving into the field.
 Overview of the topic
 Discuss resources
 Save time and effort for anyone starting out
 Purpose is NOT to be a full workshop on
data forensics
2
Outline
 History
 Where do I start learning?
 Resources
 What are threats to test security?
 How do I start deterring?
 Deterrent solutions like weblock and remote
proctoring
 How do I start detecting?
 Intro to data forensics
 Software for detection
3
History
 Literature dates before 1950
 Many collusion indices
 Most were descriptive or completely ad hoc
 Notable exception: Frary, Tideman, and Watts
(1977) – G2
 Modern era started when Wollack adapted G2
to IRT
 Other analyses not as much literature
4
5
How do I start learning?
Resources
In the past, if you wanted to learn:
1. Read all the original articles
2. Read reviews
• Bliss (2012) Covington Award – 25 indices
• Khalid, Mehmood, & Rehman (2011) – 20 indices
• Cizek 1997 book: good but little attention to
forensics
• You still need all the originals.
6
UNTIL…
Resources
Wollack &
Maynes (2013)
7
Kingston & Clark
(2014)
 You can now start here!
Overview of Security Threats
 Major sources of issues
 Brain dump makers (harvesting)
 Brain dump takers (preknowledge)
 Specific location problems
 Examinee collusion
 Receiving help (teacher, proctor, outside)
 Proxy testing
 What is your list?
8
Harvesting
9
What: Steal your
content and make it
public
Why: Often (but not
always) to make
money
How: Memorization
or images; Brain
dump sites
Deter: CAT/LOFT
Detect: Unusual
responses & latencies;
brain dump comparisons;
Trojan Horses
Minimize: Frequent
republishing
Preknowledge
10
What: Knowing
the questions and
answers
Why: Easy pass
How: Brain dump
sites (used to be
word of mouth)
Deter: CAT/LOFT
Detect: High score, low
time; brain dump
comparisons; Trojan
Horses
Minimize: Frequent
republishing
Examinee Collusion
11
What: Copying
Why: More
items correct
How: Individual
or group effort
Deter: CAT/LOFT,
multiple forms,
proctors
Detect: Collusion
indices, group
rollups
Minimize:
CAT/LOFT,
multiple forms
Receiving help
12
What: Teacher,
proctor, or
outside aid
Why: More items
correct; often
benefits the aider
How: Individual
or group effort
Deter: CAT/LOFT,
multiple forms,
proctors
Detect: Collusion
indices, group rollups,
erasure
Minimize: CAT/LOFT,
multiple forms, TEIs,
Perf tests
13
How do I start deterring?
Many options
 User roles in test development
 Limit access to test content during delivery
 Verify identity of examinee
 Test window date/time
 Test location (IP addresses)
 Lockdown browser
 Proctor/Examinee authentication
 Biometrics for ID
 Proctor training
14
Many providers
16
How do I start detecting?
It’s a Hypothesis Test!
17
 First step:
 Identify the threats you are worried about and how
you think it would present itself in data
It’s a Hypothesis Test!
 Independent variables
 Test centers/locations
 Countries
 Training programs
 Test forms
 Individuals
18
It’s a Hypothesis Test!
 Dependent variables
 Item response or test time
 Item statistics
 Test statistics (mean/SD, pass rate)
 Person statistics (intra-individual)
 Collusion indices
19
It’s a Hypothesis Test!
20
If you aim at
nothing, that’s
exactly what
you’ll hit.
It’s a Hypothesis Test!
 Example: Teachers helping kids
 Item statistics different than other teachers
 Collusion indices
 Relatively high scores with relatively short time
– bivariate plot?
 Item latencies different than other teachers
21
It’s a Hypothesis Test!
 Example: Brain dump users
 Collusion indices
 Responses on Trojan Horses
 Relatively high scores with
relatively short time
 Item latencies
 Group level not likely (could be
at any test center)
22
 Time
 High score, low time: Preknowledge or aid
 Low score, high time: Harvester
 Response patterns
 Person fit
 Score gains
23
Step 2: Determine your analysis
Options for Detection
24
Intra-Indivvidual
• Time/RTE
(CBT only)
• Response
patterns
• Score gains
• Person fit
Inter-Individual
• Collusion
Indices
• Erasure
(paper only,
also Group
level)
Group
• Roll-up of
intra and
inter
• Descriptive
Statistics
More on Collusion Indices
 How is collusion quantified? 100 item test…
 Error similarity – we both had 10 errors:
 Same items?
 Same responses on those items?
 Response similarity
 We gave the same response on 50 items? 90?
 Some indices are standardized/probabilistic (good)
 Some are descriptive or non-probabilistic (bad)
 Can vary in direction (one/two)
25
More on Collusion Indices
 There are issues to consider when
comparing:
 ESA only looks at errors, ignores rest of data
 Major confound with ability
 Two examinees with 99/100 will get flagged as
collusion!
 Therefore important to condition on this
 Some indices have no theoretical basis
whatsoever
26
More about collusion
27
Probabilistic Descriptive Ad
hoc
Error
Similarity
B&B EIC EEIC HH
HHJ
Response
Similarity
Wollack’s Omega
Wesolowsky Zjk
Frary et al G2
RIC
More resources
 ITC Guidelines on the Security of Tests,
Examinations, and Other Assessments
 TILSA Test Security Guidebook
 Conference presentations/workshops
(harder to find)
28
Software
 Next step: Find software that meets your
needs
 Scrutiny!
 S-check
 R packages (CopyDetect)
 SIFT
 Integrity
 Caveon
 IRT software like IRTPRO or Xcalibre
29
30
Epilogue: Then what?
 Define a pathway for
investigation and
actions
 Joy Matthews-Lopez
and Paul Jones
Examples (if time)
 500 certification candidates
 Gr4 Math (locations)
 Check on teachers and schools; there is
incentive to help students
31
Summary – Q&A

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Statistical detection of test fraud (data forensics) - where do I start?

  • 1. Nathan Thompson, PhD Terry Ausman Statistical Detection: Where do I start?
  • 2. Welcome!  This is some of the lessons I have learned while diving into the field.  Overview of the topic  Discuss resources  Save time and effort for anyone starting out  Purpose is NOT to be a full workshop on data forensics 2
  • 3. Outline  History  Where do I start learning?  Resources  What are threats to test security?  How do I start deterring?  Deterrent solutions like weblock and remote proctoring  How do I start detecting?  Intro to data forensics  Software for detection 3
  • 4. History  Literature dates before 1950  Many collusion indices  Most were descriptive or completely ad hoc  Notable exception: Frary, Tideman, and Watts (1977) – G2  Modern era started when Wollack adapted G2 to IRT  Other analyses not as much literature 4
  • 5. 5 How do I start learning?
  • 6. Resources In the past, if you wanted to learn: 1. Read all the original articles 2. Read reviews • Bliss (2012) Covington Award – 25 indices • Khalid, Mehmood, & Rehman (2011) – 20 indices • Cizek 1997 book: good but little attention to forensics • You still need all the originals. 6 UNTIL…
  • 7. Resources Wollack & Maynes (2013) 7 Kingston & Clark (2014)  You can now start here!
  • 8. Overview of Security Threats  Major sources of issues  Brain dump makers (harvesting)  Brain dump takers (preknowledge)  Specific location problems  Examinee collusion  Receiving help (teacher, proctor, outside)  Proxy testing  What is your list? 8
  • 9. Harvesting 9 What: Steal your content and make it public Why: Often (but not always) to make money How: Memorization or images; Brain dump sites Deter: CAT/LOFT Detect: Unusual responses & latencies; brain dump comparisons; Trojan Horses Minimize: Frequent republishing
  • 10. Preknowledge 10 What: Knowing the questions and answers Why: Easy pass How: Brain dump sites (used to be word of mouth) Deter: CAT/LOFT Detect: High score, low time; brain dump comparisons; Trojan Horses Minimize: Frequent republishing
  • 11. Examinee Collusion 11 What: Copying Why: More items correct How: Individual or group effort Deter: CAT/LOFT, multiple forms, proctors Detect: Collusion indices, group rollups Minimize: CAT/LOFT, multiple forms
  • 12. Receiving help 12 What: Teacher, proctor, or outside aid Why: More items correct; often benefits the aider How: Individual or group effort Deter: CAT/LOFT, multiple forms, proctors Detect: Collusion indices, group rollups, erasure Minimize: CAT/LOFT, multiple forms, TEIs, Perf tests
  • 13. 13 How do I start deterring?
  • 14. Many options  User roles in test development  Limit access to test content during delivery  Verify identity of examinee  Test window date/time  Test location (IP addresses)  Lockdown browser  Proctor/Examinee authentication  Biometrics for ID  Proctor training 14
  • 16. 16 How do I start detecting?
  • 17. It’s a Hypothesis Test! 17  First step:  Identify the threats you are worried about and how you think it would present itself in data
  • 18. It’s a Hypothesis Test!  Independent variables  Test centers/locations  Countries  Training programs  Test forms  Individuals 18
  • 19. It’s a Hypothesis Test!  Dependent variables  Item response or test time  Item statistics  Test statistics (mean/SD, pass rate)  Person statistics (intra-individual)  Collusion indices 19
  • 20. It’s a Hypothesis Test! 20 If you aim at nothing, that’s exactly what you’ll hit.
  • 21. It’s a Hypothesis Test!  Example: Teachers helping kids  Item statistics different than other teachers  Collusion indices  Relatively high scores with relatively short time – bivariate plot?  Item latencies different than other teachers 21
  • 22. It’s a Hypothesis Test!  Example: Brain dump users  Collusion indices  Responses on Trojan Horses  Relatively high scores with relatively short time  Item latencies  Group level not likely (could be at any test center) 22
  • 23.  Time  High score, low time: Preknowledge or aid  Low score, high time: Harvester  Response patterns  Person fit  Score gains 23 Step 2: Determine your analysis
  • 24. Options for Detection 24 Intra-Indivvidual • Time/RTE (CBT only) • Response patterns • Score gains • Person fit Inter-Individual • Collusion Indices • Erasure (paper only, also Group level) Group • Roll-up of intra and inter • Descriptive Statistics
  • 25. More on Collusion Indices  How is collusion quantified? 100 item test…  Error similarity – we both had 10 errors:  Same items?  Same responses on those items?  Response similarity  We gave the same response on 50 items? 90?  Some indices are standardized/probabilistic (good)  Some are descriptive or non-probabilistic (bad)  Can vary in direction (one/two) 25
  • 26. More on Collusion Indices  There are issues to consider when comparing:  ESA only looks at errors, ignores rest of data  Major confound with ability  Two examinees with 99/100 will get flagged as collusion!  Therefore important to condition on this  Some indices have no theoretical basis whatsoever 26
  • 27. More about collusion 27 Probabilistic Descriptive Ad hoc Error Similarity B&B EIC EEIC HH HHJ Response Similarity Wollack’s Omega Wesolowsky Zjk Frary et al G2 RIC
  • 28. More resources  ITC Guidelines on the Security of Tests, Examinations, and Other Assessments  TILSA Test Security Guidebook  Conference presentations/workshops (harder to find) 28
  • 29. Software  Next step: Find software that meets your needs  Scrutiny!  S-check  R packages (CopyDetect)  SIFT  Integrity  Caveon  IRT software like IRTPRO or Xcalibre 29
  • 30. 30 Epilogue: Then what?  Define a pathway for investigation and actions  Joy Matthews-Lopez and Paul Jones
  • 31. Examples (if time)  500 certification candidates  Gr4 Math (locations)  Check on teachers and schools; there is incentive to help students 31

Editor's Notes

  1. These are the two longest reviews I found, and have massive drawbacks… Bliss (2012) Covington Award – 25 indices regurgitated in Appendix with little/no explanation Khalid, Mehmood, & Rehman (2011) – State 20 indices but don’t even define them all (predatory journal!) Cizek had notation errors that threw me off
  2. Examples: Time: Flag an examinee for having a very low test time or average item time. Response Time Ratio is a statistic to quantify this. Response pattern: Flag an examinee for answering one option >50% of the time. In this case, they probably gave up or didn’t care and just answered “C” over and over… Score gains: Your score doubled since the last time you took the test. Not likely! Person fit: Why are you getting tough items right but easy items wrong? Collusion: A number of indices that quantify, for any given pair of examinees, whether their responses were unusually similar. Erasure: Evaluating proportion of changes that are wrong-to-right vs. right-to-wrong. Roll-up: What percent of examinees at each location/group were flagged for intra/inter issues? For example, 90% of a location gets flagged for collusion. Other stats: Some locations have high average scores but low average test times. High pass rates.
  3. As Paul Irwin said yesterday, if you don’t have policies and procedures, don’t be testing!