Classical Test Theory

By____________________

What is CCT?

X = T + E

What is “true score”?

Assumptions of CTT

Item Analysis Using CTTp – value (difficulty index)

Example How to calculate the difficulty index

discrimination index

ExampleHow 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