Recognition Versus Ability to Use External Aids: An Exploratory Item Response Analysis of the Functional External...

Item response theory (IRT) offers an alternative psychometric approach that can provide more specific measurement information beyond classical test theory (CTT). The Functional External Memory Aid Tool (FEMAT) is a performance-based assessment that evaluates everyday strategy use. Developed using CTT, the FEMAT item stems measure various compensation skills such as recognizing when to use a strategy, the ability to use a strategy, and information recall. This study aimed to investigate how the FEMAT aligns with the principles of IRT and whether IRT can provide additional insights about client performance from FEMAT item stems.

We conducted a preliminary analysis of item responses from the initial FEMAT psychometric evaluation data set (N = 99), screened for IRT assumptions, and ran a partial credit IRT model. To evaluate item stem characteristics, we completed the same IRT evaluation process and then performed analyses of variance to compare item stem difficulty across groupings.

The overall item analysis revealed a normal distribution of response categories, although some items had low frequencies in Response Categories 1 or 3. The IRT assumptions were met, with evidence of unidimensionality and local independence, and all FEMAT items fit within the acceptable range for the model. Item stems measuring recognition of when to use everyday strategies were significantly more difficult than those assessing the ability to use everyday strategies.

This IRT analysis expanded the psychometric evidence examining the FEMAT and revealed additional measurement properties of the tool. The item-level detail from the IRT analysis can inform score interpretation and identify potential areas for improvement or refinement of the measure.