Step 1
Analyze the Sampling method
In stratified sampling, the population is divided into two or more groups called strata according to some criterion such as geographic location, grade level, age, income, etc. Subsamples are randomly selected from each stratum. Elements within each stratum are homogenous but are heterogeneous across the strata. For example;
From this question, the general study is on the use of antidepressants. This is the strata, each stratum of 50 participants each based on age cuts across. They are homogenous in their individual stratum of age grades( 20-29), (30-39), (40-49) but are homogenous in the sense that 50 participants were chosen across all stratum and the study is generally about antidepressants.
Hence, the right answer is stratified sampling.
