Information can be collected by mail, telephone, personal interview, or online.

Mail questionnaires can be used to collect large amounts of information at a low cost per respondent. Respondents may give more honest answers to more personal questions on a mail questionnaire than to an unknown interviewer in person or over the phone. Also, no interviewer is involved to bias the respondent’s answers. However, mail questionnaires are not very flexible—all respondents answer the same questions in a fixed order, and the researcher cannot adapt the questionnaire based on earlier answers. Mail surveys usually take longer to complete, and the response rate—the number of people returning completed questionnaires—is often very low. Finally, the researcher often has little control over the mail questionnaire sample. Even with a good mailing list, it is hard to control who at the mailing address fills out the questionnaire.

Telephone interviewing is one of the best methods for gathering information quickly, and it provides greater flexibility than mail questionnaires. Interviewers can explain difficult questions, and they can skip some questions or probe on others depending on the answers they receive. Response rates tend to be higher than with mail questionnaires, and telephone interviewing also allows greater sample control. Interviewers can ask to speak to respondents with the desired characteristics, or even by name.

However, with telephone interviewing, the cost per respondent is higher than with mail questionnaires. Also, people may not want to discuss personal questions with an interviewer. Using an interviewer also introduces interviewer bias—the way interviewers talk, how they ask questions, and other differences may affect respondents’ answers. Finally, different interviewers may interpret and record responses differently, and under time pressures some interviewers might even cheat by recording answers without asking questions.

Personal interviewing takes two forms—individual and group interviewing. Individual interviewing involves talking with people in their homes or offices, on the street, or in shopping malls. Such interviewing is flexible. Trained interviewers can hold a respondent’s attention for a long time and can explain difficult questions. They can guide interviews, explore issues, and probe as the situation requires. They can show subjects actual products, advertisements, or packages and observe reactions and behavior. In most cases, personal interviews can be conducted fairly quickly. However, individual personal interviews may cost three to four times as much as telephone interviews.

Group interviewing consists of inviting six to ten people to gather for a few hours with a trained moderator to talk about a product, service, or organization. The participants normally are paid a small sum for attending. The meeting is held in a pleasant place and refreshments are served to foster an informal setting. The moderator encourages free and easy discussion, hoping that group interactions will bring out actual feelings and thoughts. At the same time, the moderator “focuses” the discussion—hence the name focus group interviewing. The comments are recorded through written notes or on videotapes that are studied later.

Focus group interviewing has become one of the major marketing research tools for gaining insight into consumer thoughts and feelings. However, focus group studies usually employ small sample sizes to keep time and costs down, and it may be hard to generalize from the results. Because interviewers have more freedom in personal interviews, the problem of interviewer bias is greater.

Method	Advantages	Disadvantages
Telephone Survey—a structured set of questions is recommended	Easy to carry out; fast and convenient; flexible; satisfactory response rate; people may be more willing to respond over the phone.	Can be expensive, depends on time and distance; respondents have little time to answer; body language cannot be seen; can be biased
Postal survey—a clear, detailed questionnaire is needed	Costs can be controlled; people have time to respond; any area can be covered; people may be more truthful, particularly if the reply is anonymous.	Very low response rate, i.e. the number of replies; questions cannot be explained or answers verified
Face-to-face interviews—a personal interview between the interviewer and respondent	High response rate; flexible and easily controlled; extra questions can be asked; answers can be clarified; body language can be seen	Very expensive; needs trained interviewers; can take considerable time; can be biased unless people are carefully selected
Observation—direct observation of a task or activity	Very accurate and can be easily controlled, e.g. accompanied shopping to find out what and how consumers buy	Very expensive and time-consuming needs full co-operation from the people being observed