Answer:
The study provided uses a Cluster sampling method.
Explanation:
The researcher first selects all the schools in the district.
Then he samples 5 schools from the entire district using a random number generator.
Then the researcher interviews every teacher from the 5 schools selected.
This is an example of cluster sampling.
In a Cluster sampling method, the researchers first divide the entire population into homogeneous groups, then selects a random sample of groups form the population. Then they select a random sample from each group selected.
If the researcher samples the entire groups selected then this is the case of one-stage cluster sampling and if they select a random sample of fixed size from each group selected then this a case of two-stage sampling.
Thus, the study provided uses a Cluster sampling method.