The IRT Procedure


The primary statistical assumptions that underlie the analyses that PROC IRT performs are as follows:

  • The number of latent factors is known.

  • Latent factors are normally distributed.

  • Conditional on latent factors, observed responses (items) are independent. This is the so-called local independence assumption.

These assumptions are necessary if you want to make statistical inferences. In exploratory analysis, these assumptions do not apply.