The sampling method that one would recommend in the following instances are:
1) Determining the proportion of undernourished five-year-olds in a village - Cluster sampling
2) Investigating nutritional status of preschool children. - Cluster sampling
3) Selecting maternity records for the study of previous abortions or duration of postnatal stay. - Cluster sampling
It should be noted that cluster sampling is the sampling when a researcher creates clusters or small group of the individuals with homogenous characters.
In this case, when determining the proportion of undernourished five-year-olds in a village, investigating nutritional status of preschool children, and selecting maternity records for the study of previous abortions or duration of postnatal stay, the cluster sampling should be used.
The reasons why the cluster sampling method is used in such a survey include:
The possible sampling errors that would be associated with the method is increasing the number of subjects can bring about an error of precision.
The sources of random error that may be associated with an immunization coverage survey include natural variations and environmental factors.
Finally, in the immunization coverage survey, the 30 villages are selected by system- atic sampling and the investigator uses 30 clusters that are easy to reach, the type of sampling method in this case is the cluster sampling.
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