I am using Blackboard Learning System - Vista Enterprise License
(Release Vista 8.0.3) [22.214.171.124]; and when I view assessment reports;
I am having difficulty translating the results. Specifically, the
discrimination index. I am familiar with indices from -1 to 1
indicating the difficulty of the item; but the assessment report is
reporting numbers well outside of that range. It appears to be
subtracting the lower percent from the upper percent; and reporting
that as the discrimination index. On one assessment, it reports indices
I am familiar with subtracting the lower half from the upper half;
and dividing by n; but am not sure what to do with the numbers provided
by Blackboard. Is there another step I need to take with the indices
reported? When I use the help; it says that the discrimination number
should be between -1 and 1.
Any help would be appreciated. I don't relish having to do this by hand to get my data.
In Bb Vista 8.0.x/CE 8.0.x, the "Discrimination" is displayed as a percentage whole number even though "under the hood" it's within the "-1 to 1" range. So an discrimination number of "75" is actually "0.75". It appears the Help is not really clear on how the number is displayed.
You can also go to Assessment Manger->View Reports->Overall Statistics->Run Report->View by Students->Download Records and then process the data through another statistical analysis application.
This is a good,common sense article.Very helpful to one who is just
finding the resouces about this part.It will certainly help educate me.
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