One of the most common methods to get a sample out of a population is using a simple random sample. To perform a simple random sample, each member of the population is assigned a number. Numbers are then selected at random, and whichever number is chosen that person is selected to be in the sample.
To look at how to perform a simple random sample take the following population of colored circles, number 1 – 30.
From this population, we are going to take a sample of 6 circles from the population. Using a random number generator, we get the numbers: 10, 30, 11, 14, 13, and 21. Selecting these values, we get the following sample.
Taking a second sample from the population, we’ll use the random numbers of 2, 1, 3, 27, 20, and 15. That gives us the following sample.
One of the most essential characteristics of using a simple random sample is that every single event has the same probability of happening. Now because of that, there is a risk that the sample will not accurately represent the population as a whole. For example, in the second sample, no circles from the fourth, fifth, or sixth columns were selected so the sample will not give us any information about the characteristics of those columns.