Question

Compare and contrast simple random sampling, stratified random sampling, and systematic sampling. Draw diagrams to show an example of each. What steps should be carried out to perform a simple random sample?

Answer 1

If the population is homogeneous with respect to the characteristic under study the method of simple random sampling is used to yield a homogenous sample and sample mean provided by this sample will serve as a good estimator of population mean.

While in case of heterogeneous population, we use stratified sampling in which we can reduce the heterogeneity to increase the precision of the estimator. In stratified sampling we divide the whole heterogeneous population into smaller groups or sub population, such that the sampling units are homogeneous with respect to the characteristic under study within the sub population and heterogeneous with respect to the characteristic under study among the sub population or strata. Now treat each strata as separate population and draw a sample by simple random sampling from each strata.

While systematic sampling is more convenient than the simple random sampling as well as stratified sampling. In this the first unit is selected with the help of random numbers and the remaining units are selected automatically according to the predetermined pattern.