Chi-square tests for differences in quitting smoking by birth cohort indicated that those in the oldest cohort were the most likely to have quit (Table S3)1. For example, among participants with lifetime FTND, 49.2 % of those born before 1945 had quit, compared with 22.4% of those born between 1945 and 1975 and 15.5% of those born after 1975. To determine whether these differences were due to measurement non-invariance rather than other causes, regression models were created with and without accounting for non-invariance (Table 3). In baseline models for the birth cohort (using birth cohort 1945–1975), higher lifetime FTND scores were associated with less quitting, as expected (odds ratio =0.48, 95% confidence interval [CI] =0.40–0.44, p<.001). After adjusting for measurement non-invariance, the odds ratio and 95% CI estimates did not change.
