Purpose

The questionnaire (also called survey) is a set of questions given to a sample of people. The purpose is to gather information about the people’s attitudes, thoughts, behaviors, and so forth. The researchers compile the answers of the people in the sample in order to know how the group as a whole thinks or behaves. 

Questionnaires are often used by people who do political or market research. For example, if a politician wanted to know what voters thought about a particular issue, he or she could do a survey. The survey would ask about the voters’ opinions related to the issue.

A new business might want to send a questionnaire to potential customers, to see what people like. A restaurant could ask about people’s preferences for tastes, price, service, and restaurant appearance.

Population and random sample

The person gathering the data has a group of people he or she wants to study. In the case of a U.S. senator, the group is all of the people living in his or her state. This large group—the group of all the people the researcher wants to know about—is called the population. If the senator from Virginia wanted to know what voters were thinking, the population would be all voters in the state of Virginia.

However, it would be impractical to send a questionnaire to every voter in the state. Instead, the researcher doing the study would use a smaller set of people from the state. This smaller group is called the sample.

The sample needs to be representative of the population. In other words, the sample needs to be like the population in every aspect. If 60% of the state’s voters are women, then 60% of the sample needs to be women. If 30% of the state’s voters are farmers, then 30% of the sample must be farmers.

To ensure that the sample does represent the population, researchers use a random sample. A random sample means that every person in the population was equally likely to be chosen. Picture a huge hat with the name of every voter on a slip of paper inside. The researcher needs to reach into that hat and pull out 500 names one by one. This is a random sample. When the sample is chosen randomly, it will reflect the characteristics of the population.

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Advantage

1. Using a questionnaire with a random sample is a good way to find out the attitudes, thoughts, and behaviors of a large group of people. We can be more confident in generalizing our findings than we can be with a case study.  In other words, because we have a group of people (random sample) instead of one case, we are more sure that the findings apply to the population.

A questionnaire provides better data for politicians or businesses to use for making decisions. If the senator learns that 75% of the people in the random sample of voters favor a proposed law, he or she can be confident that essentially 75% of all the voters in the state also favor the proposed law. This is more useful information than a case study of one voter.

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Disadvantages

There are two elements of a questionnaire that are not so much disadvantages as potential problem areas.

1. The way a question is worded can change how people answer the question. A question that asks for an opinion about “tax breaks for small businesses” would yield different responses than an opinion question about “corporate welfare.” When you read about the results of a survey or questionnaire, it’s important to know exactly how the question was phrased.

2. Getting a random sample of people from the population can be difficult, so sometimes people doing surveys do not get a random sample. It is much easier to go to a shopping mall or diner and ask people their opinions of a proposed law than to generate a random sample of voters in the state. When you read about the results of a study using a questionnaire, it is important to know whether the participants were a random sample.  

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Read a questionnaire sample.