The IRT Procedure (Experimental)
The primary statistical assumptions that underlie the analyses that PROC IRT performs are as follows:
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The number of latent factors is known.
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Latent factors are assumed to be normally distributed.
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Conditional on latent factors, observed responses (items) are assumed to be independent. This is the so called local independence assumption.
These assumptions are necessary if you want to make statistical inferences. For exploratory analysis, these assumptions do not apply.