I am using Blackboard Learning System - Vista Enterprise License (Release Vista 8.0.3) [18.0.3.74]; 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 from 0-75.
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.
Colleen
Hi Collen,
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.
Cheers,
Bob
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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