The Happier Lives Institute estimates an effect size of ~0.8 for StrongMinds' intervention. An upcoming RCT, run by Berk Ozler, will give more data on how well their intervention works.

Gregory Lewis, commenting on the Happier Lives Institute's fundraiser, strongly expects that this study will return a smaller effect size than past studies (some of which are very old, and some of which were run by StrongMinds themselves), and raises other criticisms of the Happier Lives Institute's approach:

I think we can be pretty sure (cf.) the forthcoming strongminds RCT (the one not conducted by Strongminds themselves, which allegedly found an effect size of d = 1.72 [!?]) will give dramatically worse results than HLI's evaluation would predict - i.e. somewhere between 'null' and '2x cash transfers' rather than 'several times better than cash transfers, and credibly better than GW top charities.' [I'll donate 5k USD if the Ozler RCT reports an effect size greater than d = 0.4 - 2x smaller than HLI's estimate of ~ 0.8, and below the bottom 0.1% of their monte carlo runs.]

Market on whether the RCT is above a threshold: