@tomaszaba I noticed that the way IPC calculates prevalence based on what you have been showing in your approach is that no survey weights are being applied to account for the cluster design of the survey/s that produced the data. For example, in your South Sudan example, you basically just calculate prevalence by doing a simple number of SAM divided by total number of kids in sample.
Does IPC just automatically assume that the PPS done at the start was followed strictly as per design? From my experience, very rarely do survey data come up as designed and samples per cluster is never always what is expected. For S3M and RAM type surveys that Mark and I have developed, this doesn't matter too much as we always do weighting posteriorly (we don't do PPS). But, for a PPS design in which the weights are applied right from the sampling itself, having a sample that is different from your intended design has implications in the balance of your dataset such that a simple number of SAM cases divided by all 6-59 in sample will give biased results.
Do you guys don't do any weighting at all on the data to calculate prevalence?