dif1.txt
File contains 2,000 cases and 65 items. It also includes and ID and GROUP
variable.

Data were simulated. There is no missing data.

Answer key (Format = Response Option: Item numbers)
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1. Items V2 - V61 are coded as 0 or 1. These are binary items.
   The correct answer is 1.
2. Items V62 - V66 are coded 0, 1, 2, or 3. These are polytomous items.
   The scores are the same as the codes: 0, 1, 2, and 3.