Assessing the Inclusion of Foil Items in a Scale to Measure Recognition of Health Messages.

Researchers frequently measure recognition of information in health messages by presenting participants with statements that were or were not in a message and then asking them to identify which were presented and which were not. Recognition scales are then calculated by summing the correct responses to both the true items and foils, or by summing the correct responses to the true items only. We used a sequence of psychometric analyses, including factor analysis and item response theory (IRT) analysis, to evaluate two recognition measures of this type, using data from previously published studies. We found that foils are less associated with true items than true items are with one another, or more practically, that foils are less associated with the underlying dimension of interest. These results provide researchers with insight into how recognition items function, as well as a better analytic approach for use in future studies.