Answer to Question #277112 in Algorithms for hhh

Question

In the population, there are three major classes. People are classified into either class A (10% of the population), class B (60% of the population) or class C (30% of the population). When we pick samples from the population, we can apply (a) random sampling or (b) stratified sampling. Explain both sampling techniques using this scenario.

Answer 1

In a random sample, we choose people without paying attention to which class they belong to. So, with a sample of size 10, we, on average, should get one person of class A, six of class B, and three of class C. But a specific sample may not contain representatives of class A at all, and classes B and C can be represented in equal numbers.

With a stratified sample, we select one representative from class A, six representatives from class B, and three from class C.