The main research question is whether smoking quantity and nicotine dependence have time-varying effects on smoking frequency. The motivation for obtaining effect sizes is to supplement results from a previously run mixed-effects regression model investigating these variables’ interactions with time (among other terms). Random effects included slope and intercept which were allowed to vary by subject. The analysis showed significant time-varying effects; that is, the strengths of associations that smoking quantity and nicotine dependence score have with smoking frequency change over time. For this reason, obtaining local effect sizes for (1) smoking quantity and (2) the nicotine dependence score within each assessment wave is helpful to better characterize exactly how their relationships with smoking frequency change over time as well as how they compare to each other. Since evaluating effect sizes within each assessment wave no longer involves repeated measures, there are no random effects to fix and thus the reduction in variance is purely due to the fixed effects.
