Item response theory

Question 1

Theta

Answer 1

Value used to indicate trait level

Question 2

Item Difficulty

Answer 2

The hight of a traint level needed to be answered correctly. Indicated with value Beta (B)

Question 3

Item Discrimination

Answer 3

Degree to which an item can differentiate between two values on one side of the scale. 0 means it’s not related to construct, high is consistent. Noted with alpha (a)

Question 4

Cause of low discrimination (a)

Answer 4

for example when an item requires more than just knowledge of the trait it measures. Eg on a math test, knowledge of certain words.

Question 5

Guessing

Answer 5

Answering correctly on the basis of chance/guessing. Should be corrected for. Indicated by c (c)

Question 6

CTT problems

Answer 6

It’s focused on the test, not on the items.

Test properties depend on the population. eg reliability, the difficulty etc.

Person properties depend on the test.
Eg easy exam vs difficult exam result in diff sum scores, for which different assumptions

Question 7

Modern test theory

Answer 7

Specifies a measurement that links the construct (the latent variable) to the item scores.