Minimum detectable effect size for main outcomes (accounting for sample
design and clustering)
For ratings in the post-truth arm, we are powered to detect 0.14 SD of the difference between the rating in the (wrong, agree) cell vs the rating in the (wrong, disagree) cell (per database or combined across databases). This is well below the smallest (0.62 SD) effect size we saw in the pilot. We are also powered for other comparisons of interest such as the difference between the rating in the (correct, agree) cell vs the rating in the (correct, disagree) cell, or [(correct, agree) - (correct, disagree)] - [(wrong, agree) - (wrong, disagree)].
For our secondary outcomes, with N=800 attentive respondents and pre-registered controls, we are powered to detect effects of roughly 0.16–0.25 per database.