Hi Charles,

Our takeaway from this data is that there is not evidence of an effect (positive or negative).

We take these data to be our best guess because there are no prior studies of the effect of deworming on SWB, and the evidence of impact on other outcomes is very uncertain. However, all the effects are non-significant. We don’t have a theory of action because we think the overall evidence points to there being no effect (or at least just a very small one).

We ran the cost-effectiveness analysis as an exercise to see how deworming would look if we took the data at face-value. The point estimate was negative, but the confidence interval was so wide that the results were essentially uninformative, which converges with our conclusion that there is not a substantial effect of deworming on long-term wellbeing. 

That being said, we can make assumptions that are favorable to deworming, such as assuming the effect cannot be negative. This, of course, involves overriding the data with prior beliefs — prior beliefs that we lack strong reasons to hold. In any case, we explore the results under these favorable assumptions in Appendix A2. In all plausible cases,  deworming is still less cost-effective than StrongMinds, so even these exploratory analyses —which, again, we don’t endorse— don’t change our conclusion to not recommend deworming over StrongMinds. 

Regarding power

Trying to draw conclusions from such a dramatically underpowered study (with regard to this question) strikes me as absurd.

It is unclear what evidence you use to claim the study is underpowered. As Joel mentioned in his comment to MichaelStJules (repasted below), we had 98% power to detect effect sizes of 0.08 SDs, the effect size that would make deworming more cost-effective than StrongMinds . 

Assuming (generously) that the effects of deworming couldn't become negative, then the initial would need to be 0.08 SDs for deworming to beat StrongMinds, which we had 98% power to detect.