A critical first step in the IDA framework for developing commensurate measures is to conduct a feasibility analysis. This involves assessing the extent of between-study heterogeneity in measurement by defining the measurement scenario present in the pooled data design and evaluating whether and how the construct(s) of interest are measured in each study. IDA requires that at least some common items are present across studies, where common items may be either identical or harmonized items. Common items allow us to link measures across studies. Common items may be present in all studies or only pairs of studies, so long as sufficient pairs exist with which to link measurement across studies (e.g., Studies 1 and 2 share items and Studies 2 and 3 share items such that measurement in Studies 1 and 3 can be linked through Study 2). Unique items, or items present in only one study, do not help in linking measures, but still provide useful information for estimating participants’ scale scores and more fully assessing constructs of interest. In our example, all three studies included at least one measure of internalizing behavior, with some overlap in item content.
