Random Sample in Psychology: Example & Definition

Suppose you wanted to research the effects of receiving a bad grade on the morale of 100 high school freshmen. You might assign each student a number from 1-100, place the numbers in a hat, then choose 30 numbers from the hat to be in your sample. This is known as the lottery method. Because every person has the same chance of being picked, it helps make sure that all possible biases and viewpoints are represented. Since each number was only placed on one piece of paper and all the papers were the same size, each person had the same chance of being picked. Also, since the numbers were written on separate sheets of paper, the selection of one person was not dependent on the selection of another.

Advantages and Disadvantages

There are several advantages to using a random sample, including:

• It's highly representative of the population
• It decreases bias since the process of selecting the sample is done randomly
• Data analysis and interpretation is simpler in random samples

There are also several disadvantages to using a random sample, including:

• It's not possible if you do not have a complete list of the members in the population
• It can take a lot of time and money if you are sampling data from a large population
• The characteristics of the sample and/or the population can change over time

Lesson Summary

Let's review. In a random sample, each member of the population has the same probability of being selected for the sample. In addition, the selection of one member of the population is completely independent of the selection of another. There are several advantages to using a random sample including a decrease in bias and having data that is highly representative of the population. There are also disadvantages, including the potential costs, time that it may take to find a truly representative sample, and the difficulty of creating a complete list of all members in a population.