Follow-up behavior change analyses
To explore whether the main findings, i.e., changes in drinking occasion frequency from active to inactive weeks differed from non intervention-related changes, we compared drinking frequency change scores among participants in the interventions and the control condition. For each person, we calculated a change score that captures differences in the average proportion of drinking occasions on active intervention weeks versus inactive weeks throughout the 28-day study period. First, we first calculated the average proportion of drinking occasions on active weeks and inactive weeks, separately, by dividing the number of drinks reported throughout the active and inactive intervention period by an individual’s number of responses to alcohol reminders during the same time period. Next, we subtracted the proportion of drinking occasions on active weeks from the proportion of drinking occasions on inactive weeks.To obtain change scores for participants in the control condition, who did not undergo a within-person active-to-inactive week manipulation as part of the protocol, we randomly assigned two of the four weeks in the study period as pseudo “active” and the remaining two as pseudo “inactive” weeks. To counterbalance week order, as done in the active treatment groups, we randomly split half of the participants in an ABAB design, or a BABA design, which allowed us to match the two intervention designs as closely as possible. We repeated this random assignment 100 times to stabilize the estimates. Next, we averaged the change scores in drinking frequency (from pseudo-inactive to pseudo-active weeks) for the control participants across all iterations and compared the control group’s pseudo change scores to the intervention groups’ change scores. We first checked whether the proportion of drinking occasions were significantly non-Gaussian using the Shapiro Wilk test of normality and chose to perform non-parametric Mann–Whitney–Wilcoxon tests instead of t-tests because of nonnormality. We performed this comparison using unpaired two-sided Wilcoxon tests.