H3) The devaluation of unhealthy items’ ratings mediates the reduction in unhealthy item consumption
For H3, according to Vittinghoff, Sen, and McCulloch’s methodA total of 210 participants is thus required to reach 0.95 power across all our contrasts. However, as the study was fully online, we could have reached a much larger sample size and potentially detected small, irrelevant effects. Hence, we decided to include additional criteria of minimum effect size for significant results to be interpreted. For H1, H1a, and H1b, we only interpreted a minimum mean difference of 5/100 between the control and experimental groups. For H2, the standardised effect size of interest (i.e., partial Cohen’s f) must reach at least 0.25 for the group-by-session interaction of our within-between ANOVA, corresponding to a medium effectShould have we reached a higher sample size as the minimally required sample size, we would have stopped inclusion in the study at a total of n = 300.The ‘Analysis plan’ below details the exclusion rules for data analysis and how they would affect our sampling plan.