Video Transcript
In a certain survey about the
colleges that some high-school students wish to join, a sample of 2,000 students was
randomly selected out of a population of 40,000. Is that considered to be stratified
sampling?
To answer this question, let’s
remind ourselves of what we mean by stratified or layered random sampling. This is a sampling method we use
when the population consists of nonoverlapping subdivisions or strata. To select a stratified random
sample from a population, we take random samples from each stratum proportional to
the size of that stratum within the population. In this example, we’re told that
our population size is 40,000 and that a sample of 2,000 students was randomly
selected. We have no information on whether
or not the population was subdivided into strata. And so we must assume that the
random sample of 2,000 students was selected directly from the population where
there were no strata involved. We cannot then say that this
involves stratified sampling. Our answer must then be no, this is
not stratified sampling.