Chapter 2 Section 2 Surveys, Samples, and Populations Obj: Explain the survey method and the importance of proper sampling techniques.

The Survey Method Gathering information by asking people directly is usually accomplished by means of a survey. In a survey, people are asked to respond to a series of questions about a particular subject.

Psychologists conduct surveys by asking people to fill out written questionnaires or by interviewing people orally. By distributing questionnaires or by conducting interviews over the telephones or in person, researchers can rapidly survey thousands of people. Computers often aid in the analysis of the information collected.

The findings of interviews and questionnaires are not necessarily completely accurate. People may not be honest, for whatever reasons, about their attitudes or behavior. Some people may fear that their responses will not be kept confidential. Thus, they answer only what they are willing to reveal to the world at large. Other respondents may try to please the interviewers by saying what they think the interviewers want to hear.

Populations and Samples When researchers conduct any type of study, they must consider what group or groups of people they wish to examine and how respondents will be selected. This is particularly true with surveys.

To accurately predict an outcome, it is necessary to study a group that represents the target population. A target population is the whole group you want to study or describe. It would be costly and difficult – if not impossible – to interview or question every member of a target population (in this case, all voters in the area). Instead, researchers study a sample, which is only part of the target population.

Selecting Samples Psychologists and other scientists select samples scientifically to ensure that the samples accurately represent the populations they are supposed to represent. In other words, a sample should be as similar as possible to the target population. Otherwise, researchers will be unable to use the sample to make accurate predictions about the population from which the sample is drawn.

One way that scientists obtain a sample that they hope represents the target population is by using a random sample. In a random sample, individuals are selected by chance from the target population. Each member of the population has an equal chance of being chosen. If the random sample is big enough, chances are that it will accurately represent the whole population.

Researchers can also use a stratified sample. In a stratified sample, subgroups in the population are represented proportionally in the sample. For instance, about 12 percent of the American population is African American. A stratified sample of the American population would thus be about 12 percent African American. A large random sample is likely to be accurately stratified even if researchers take no special steps to ensure that it is.

Generalizing Results Sometimes, for one reason or another, researchers do not use a sample that represents an entire population. In some cases, the researchers want to know about only one group within the population and thus have no reason to study other groups. In other cases, it may be impractical or impossible to obtain a random or stratified sample.

Researchers cannot learn about the preferences of all people by studying only one group of people, such as men. The gender of the individuals in the sample is not the only characteristic that researchers must take into account.

Volunteer Bias Researchers often have little control over who responds to surveys or participates in research studies. Although the researchers may choose to whom they give a questionnaire, they usually cannot force people to complete the questionnaire. Another factor that psychologists must take into account is bias, or a predisposition to a certain point of view. People who volunteer to participate in studies often bring with them a volunteer bias – that is, they often have a different outlook from people who do not volunteer for research studies.

For one thing, volunteers are usually more willing than other people to disclose personal information. Volunteers may also be more interested in research than people who do not volunteer. Furthermore, they may have more spare time to participate in research studies than other people. Depending on what the study is about, any or all of these factors – as well as others – could skew the results. That is, these factors could slant the results in a particular direction.