Transcript Classical Test Theory - Georgia State University

Classical Test Theory
By
____________________
What is CCT?
X=T+E
What is “true score”?
Assumptions of CTT
Item Analysis Using CTT
p – value (difficulty index)
Example
How to calculate the difficulty index
discrimination index
Example
How to calculate discrimination index
How do you improve a test
by conducting the item analysis in CTT?
“Group dependent” item analysis
What is reliability?
Procedures for estimating reliability
• Test – retest reliability
• Alternate forms reliability
• Internal consistency (split-half, KR-20,
coefficient alpha)
What is standard error of
measurement (SEM)?
SEM is the same for all the examinees
because
The formula for SEM is
Example
• Reliability = .91
• SD = 10
• Then, SEM is ____________
Limitations of CTT
Conclusion