nicotine dependence level, results in estimates of response differences attributable to measurement non-invariance. Models including direct paths from each birth cohort to each FTND item were compared to nested models, where direct paths were fixed to zero using Mplus difftest to determine the statistical significance of non-invariance (Muthén and Muthén, 1998–2015). Separate models were run with different reference groups to examine all pairwise differences (e.g., birth cohorts 2 and 3 vs. 1; birth cohorts 1 and 3 vs. 2). Results for other reference groups are presented in the Supplementary Material. For significant item-level invariance (direct-path parameter estimates with p<0.05 in the final model), eta-squared (r2) effect sizes were calculated (Ferguson, 1966).
