Fri, 22 Feb 2008 21:32:43 +0100
I have run across the Kuder-Richardson statistic in loncapa. Does
anybody have experience with that?
As I understand it is a measure of reliabilty of a test.
I have computed this statistic for two assessments. In both tests scores
per test item are either 0 or 1.
Assessment 1: 22 test items
fall 2006 kr-21=0.82
spring 2007 kr-21=0.81
fall 2007 kr-21=0.82
Assessment 2: 27 test items
fall 2007 kr-21=0.73
spring 2008 kr-21=0.74
The last assessment has been retaken after two weeks of additional
training, resulting in kr-21=0.76 (with better overall results).
What do these data tell me?
Is assessment 1 considerably more reliable than assessment 2?
An what does it mean that an assessment is less reliable?
I guess that low reliability means that one will likely get a different
distribution of scores if one repeats the assessment.
If I did my algebra correctly, kr-21=1 for coin flipping. The maximum
value of kr-21 is k/(k-1) ~ 1. So, if I want to have reliable
assessments I ask my students to flip a coin???
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