Posted by
Swank, Paul R on
Nov 18, 2011; 5:08pm
URL: http://spssx-discussion.165.s1.nabble.com/question-about-measure-creation-statistics-tp5002888p5004950.html
Explain what you mean by the answers are not dichotomous. A multiple choice knowledge question has a right answer and several wrong answers but the scoring is dichotomous, right (=1) wrong (=0). Cronbach's alpha in this case gives exactly the same result as the KR-20. It is just a generalization of the Kr-20 to items that are not dichotomous. As the other Paul said, the KR-21 has unreasonable assumptions and was only used because at the time they were developed (1930s) simplicity of computation was of concern. In other words, your advisor is wrong.
Paul
Dr. Paul R. Swank,
Children's Learning Institute
Professor, Department of Pediatrics, Medical School
Adjunct Professor, School of Public Health
University of Texas Health Science Center-Houston
-----Original Message-----
From: SPSSX(r) Discussion [mailto:
[hidden email]] On Behalf Of mmiesner
Sent: Thursday, November 17, 2011 6:47 PM
To:
[hidden email]
Subject: question about measure creation statistics
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
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