1B
CONSTRUCTING THE SURVEY PROTOCOL
Cluster sampling It is sometimes too expensive to spread a sample across the entire population. There is a risk that travel costs may become high when the surveyors need to survey people from one end of the selected area to another. The technique of cluster sampling helps to reduce costs. The method of Cluster population
cluster sampling is to divide the population into sub-groups also called “clusters”. Not all these groups are selected: only a certain number of clusters are randomly selected to represent the target population. All units within the selected clusters are included in the sample (i.e. all people in these clusters are interviewed).
Cluster Sampling
1st degree
Population in primary unit
Sample Random sampling of primary units
General population
2nd degree
Sample of primary units Random sampling of secondary units
3rd degree
Sample of secondary units
Example of multistage sampling:
Most of the time the clusters are formed naturally and not by reference to a criterion, unlike strata. Clusters can be educational institutions, villages, health facilities etc.
Multistage sampling Multistage sampling is a combination of the methods of random sampling outlined above, and the method chosen may vary to some degree. This type of EN 20
selection is one that guarantees the greatest representativity for the survey vis-à-vis the target group and the validity of results but it is also one of the most complex methods.
In practice, when the conducting KAP surveys, we most commonly use the method of multistage sampling. For example, we will first carry out a cluster sampling to randomly select villages to be included in the survey (1st stage). Then, from the selected villages, households are selected to be included in the survey (2nd stage). This can be
achieved using such systematic sampling, for example, whereby households are selected at regular intervals and calculated. Surveyors may follow, for example, the following protocol: > Identify the number of village in the previously defined health area (e.g. coverage area of a mobile team) and randomly select the villages (1st stage);
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