We also believe that the IDA framework may have broader implications for other types of research designs. For example, what constitutes an “independent” study contributing to a pooled data analysis can sometimes be unambiguously determined and other times cannot. In some cases, minor design differences between samples may be present. For example, independent samples may be collected within a multi-site or rolling recruiting single-site design in which key design characteristics are held constant (e.g., recruitment, procedures, measurement) yet each study is conducted in a different setting (e.g., different hospitals or regions of country) or across different time periods (e.g., as recruitment rolls across different school years or birth cohorts). These independent samples are then pooled for analysis with some control for site or cohort differences (e.g., Kaplow et al., 2002; Stark et al. 2005). In other cases, many design differences between samples may be present. For example, multiple independent samples may each be collected as part of a different independent studies that were conducted at different historical times using different sampling mechanisms, experimental procedures, and psychometric instruments. Thus what constitutes
