Response to Another Student Discussion-U5D2-Analyze This Thing: What Is a Good Item?

u05d02-Leillanie Delacruz

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Hello All,

 According to Cohen, Swedilk, & Sturman (2010), an item-difficulty index is deemed optimal at p=.60 for a five- option multiple choice item and p=.75 for a two option (true or false) item.  In the item-discrimination index the higher the value the more it distinguishes between high and low score examinees.  If the value is a negative, there is more of a chance of the low scoring examinees to answer the item correctly than a high scoring examinee. 

Based on the THING test, Item 2 shows an optimal difficulty between items with a p=.60 on the item difficulty index and some discrimination between examinees d=.20 on the item-discrimination index.  The item can still be used but Item 3 would be the most ideal with p=.60, which is the optimal item difficulty on a five-option multiple choice item, and a d=.60 on the item-discrimination index that shows a higher discrimination between high and low scoring examinees.

Item 1 indicates that it is too easy with an item-difficulty index of p=1.00 signifying that everyone that took that test got the answers correctly. The item-discrimination index is a d=0.00 which indicates that there was no discrimination between the examinees that usually score high and those that score low

Item 4, although it shows an optimal difficulty, p=.60, it has an item-discrimination index of d=-.100 indicating that low-scoring examinees are more likely to get that question correctly than their high-scoring peers, therefore, I would also eliminate this item

Reference:

 Cohen, R. J., Swerdlik, M. E., & Sturman, E. (2012). Psychological testing and assessment: an introduction to tests and measurement. New York, NY: McGraw-Hill.

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