What is the Difference Between Population and Sample?

Sample Size

In the methodology section of your dissertation you will be required to provide details about both the population and sample of your study. These sections are a common stumbling block for many students, as students often fail to properly distinguish between the two. So, what exactly is the difference between the population and sample?


First, your sample is the group of individuals who actually participate in your study. These are the individuals who you end up interviewing (e.g., in a qualitative study) or who actually complete your survey (e.g., in a quantitative study). People who could have been participants in your study but did not actually participate are not considered part of your sample. For example, say you e-mailed study invitations to 200 people on a listserv and 100 of them end up participating in your study (i.e., complete your survey or your experiment). Your sample is the 100 individuals who participated in your study. The 100 individuals who received invitations but did not participate would not be considered part of your sample; rather, they are part of what is often called the sampling frame. Your sampling frame is the group of individuals who could possibly be in your study, which in the above example would be the 200 individuals on the e-mail listserv.

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On the other hand, your population is the broader group of people to whom you intend to generalize the results of your study. Your sample will always be a subset of your population. Your exact population will depend on the scope of your study. For instance, say your research question asks if there is an association between emotional intelligence and job satisfaction in nurses. In this case, your population might be nurses in the United States. However, if the scope of your study is more narrow (e.g., if your study deals with a local problem or a specific specialty/industry), then your population would be more specific, such as “nurses in the state of Florida” or “licensed practical nurses in the United States.” Importantly, your population should only include people to whom your results will apply. For example, if you do not have good reason to believe that your results will apply to all nurses in the United States, then your population will need to be more specific. If you are stuck on defining your population, think about how you would fill in the blank in the following sentence: “The results of my study will apply to _____.” Your answer will help determine how you define your population.

To summarize: your sample is the group of individuals who participate in your study, and your population is the broader group of people to whom your results will apply. As an analogy, you can think of your sample as an aquarium and your population as the ocean. Your sample is small portion of a vaster ocean that you are attempting to understand. Properly distinguishing between these two concepts will aid you as you navigate the methodological details of your dissertation.