Answer;
-Stratified sampling
Explanation;
-A Stratified Sample is sample in which the population is divided into mutually exclusive groups, or strata and randomly drawn from each of these groups.
-With stratified sampling, the researcher divides the population into separate groups, called strata. Then, a probability sample (often a simple random sample ) is drawn from each group.
-Using stratified sampling, it may be possible to reduce the sample size required to achieve a given precision. Or it may be possible to increase the precision with the same sample size.
