Statistical analysis
Anxiety
CORONAVIRUS
We aimed to recruit 80 participants (n = 40 per group). Group sizes are powered to observe a significant interaction between time (within-person) and treatment (between-group) using a mixed model. Assuming a medium-sized (d = 0.4), group sizes of 21 are powered at 80% to observe a significant group-by-time interaction (alpha = 0.05, calculated using G*Power v3.1.9.7). Analyses were completed in RStudio v2022.02.3 [For each outcome, the full model was compared to a reduced model, which omitted any effects of group or group-time interactions. Reduced models included a random intercept for each participant and dummy variables for time only. This allowed us to model the impact of treatment for each time point regardless of group. Full and reduced models were compared using Analysis of Variance (ANOVA). In cases where the models did not differ (i.e., in variability explained), results from the reduced models are presented only.Age was included as a covariate in all models. Given the broader study context, we repeated our analyses with the Coronavirus Anxiety Scale [