Estimation of items

Question 1

Difficulty estimates

Answer 1

Can be positive and negative. It’s just the location on the graph. However, very high numbers mean they’re either really easy or really difficult. Not useful.

Question 2

Discriminant estimates

Answer 2

Contra indicative items result in negative discriminant estimates. These should be rewritten.

Therefore these estimates should be positive.
I they’re close to 0 or even little negative: poor items. Don;t discriminate

Question 3

Norm reference

Answer 3

You’re comparing to the calculation so you want the test curve to by very broad

Question 4

Criterion reference

Answer 4

You want to discriminate at the cut off point, so you want the testcurve to be highly focused around the criterion with a lot of discrimination.