A questionnaire consists of a set of questions presented to respondents. Because of its flexibility,it is by far the most common instrument used to collect primary data. Researchers need to carefully develop,test,and debug questionnaires before administering them on a large scale. The form, wording, and sequence of the question can all influence the response.Closed-end questions specify all the possible answers and provide answers that are easier to interpret and tabulate. Open-end questions allow respondents to answer in their own words and often reveal more about how people think. They are especially useful in exploratory researcher, where the researcher is looking for insight into how people think rather than measuring how many people think a certain way. Table 4.1 provides examples of both types of questions;also see "Marketing memo:Questionnaire Dos and Don'ts.