Minimum detectable effect size for main outcomes (accounting for sample
design and clustering)
Using billing data from 2017-2021, we calculate the mean probability of on-time payment has been 61.5%. The mean arrears as of February 2021 among customers is 3,248 KSH (std dev= 10,732 KSH). With these priors, the sample sizes given above, and a power of 80%, the minimum detectable difference in the probability of on-time payment is 1.92 percentage points. The minimum detectable effect size on the total balance of arrears is Ksh 425.