question about measure creation statistics

Posted by mmiesner on Nov 18, 2011; 12:47am
URL: http://spssx-discussion.165.s1.nabble.com/question-about-measure-creation-statistics-tp5002888.html

Hello-
I'm creating a measure that currently has 20 items. 18 of these items are multiple choice, 4 possible answer questions. 2 of the items have 7 possible answers. All of the items are covering the same broad area (knowledge of psychological disorder criteria).

I ran cronbach's alpha and the score was .78.
I talked to my advisor, who said this was incorrect and I should have run KR-20. I did some reading, and two things appear to be true.

First, that in fact, I should be using KR-21 since the answers are not dichotomous.
Second, that there is no way to do this in SPSS.

Would LOVE some guidance.

Michael