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I'm trying to use IRT to select the best items for a one-factor scale that has 20 items. I was wondering what I need to be looking at if I wanted to select 5 or so items from these items (for a short version of the scale). I would really appreciate any suggestions/references!

llbia
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Higher slope values are better - this are discrimination parameters, the higher the slope, the greater the ability of the item to distinguish ability.

A range of difficulty parameters - or difficulty parameters in the area where you want the measure to have the most precision.

Jeremy Miles
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  • thanks! I'm wondering whether there are some criteria; Also, can the slopes be too high? some of my items have slopes going up to 6.5 and I'm not sure if it's always the higher the better... – llbia May 18 '20 at 13:34
  • Ah, yes, slopes can be too high. This is often caused by two items that are highly related (essentially the same item repeated twice) and is caused by a local dependency. – Jeremy Miles May 18 '20 at 15:44