For a SLEAC assessment the Health District should be taken as the Sampling Zone. Within each Health District a sample size (n) of 40 SAM /MAM Cases should be applied as a rule of thumb. This sample size is large enough for there to be a very small amount of errors in the final coverage classification.
The selection of villages or communities to sample during a SLEAC survey follows exactly the same steps as the planning of a likelihood survey in a SQUEAC.
Based on the required sample size (i.e. the number of cases of acute malnutrition that need to be identified), the following formula can be used to calculate the number of villages or communities to visit (n=recommended sample size):
For example, if:
Target sample size (n) = 41
Average village population (all ages) = 600
Prevalence of SAM = 1%
Percentage of children aged between 6 and 59 months = 20%
The minimum number of villages to be sampled would be:
With this information, the surveyors need to select the villages they need to sample in a random way. There are two methods which can be employed to do this:
Centric Systematic Area Sampling method: this involves taking a spatially stratified sample of the health district being investigated by drawing a grid of equally sized squares (‘quadrats’) over the area to be sampled and sampling the community or communities located closest to the centre of each square. This method requires a large printed map of the health district marked with every known village or community. More information is available here.
Spatially stratified sampling method: if no map is available containing all known villages or communities, this method can be used to select the villages. All villages or communities need to be listed by health centre catchment area. More information is available here.