Informal observation can help in narrowing a marketing problem. However, it can lead to sampling errors. You can use a survey to collect data by asking the target population a series of questions. To question the sample respondents over time, marketers use a panel , a group of people who participate in a series of surveys. This also allows marketers to establish a dialogue with respondents.
Limited contact reduces the possibility of bias.
Bias may result when a researcher reveals emotional reactions, leading some respondents to modify their answers. Lengthy questionnaires are not appropriate. Personal surveys provide in-depth answers, meeting respondents face to face. In a focus group interview , a researcher meets with a group so 8 to 12 people to discuss a particular product or topic. Interviews may be videotaped or audiotaped.