Benjamin wants to conduct a survey about students’ favorite sports in his school. He randomly selects a sample of 30 students. Is that considered stratified sampling?
To answer this question, let’s see how we define stratified sampling and see if this fits with Benjamin’s sampling method. We use stratified random sampling when a population naturally subdivides into nonoverlapping groups or strata. A random sample is then taken from each stratum in the proportion of that stratum within the population. These individual samples then combine to form one representative sample.
We’re told that Benjamin randomly selects a sample of 30 students from his school. And since we have no other information, we must assume that Benjamin randomly selected his sample directly from the population and that the population were not first subdivided into strata before sampling. This does not match with our definition of stratified random sampling. And since Benjamin’s sample was taken directly from the population without subdividing, this is not considered stratified sampling. Our answer to the question then is no.