Open-ended questions are those that provide respondents with a question prompt and provide them a space in which to construct their own response. Closed-ended questions, alternatively, provide a question prompt and ask respondents to choose from a list of possible responses. Factors relating to both the researcher and respondent are important to selecting which question format to utilize.
Current knowledge of phenomenon: One of the strengths of open-ended questions is that they allow for the discovery of unanticipated responses. This makes them particularly useful in the exploratory stages of questionnaire construction. For example, suppose a researcher is studying the habits of college students, with a particular focus on how their time out of class is spent. If the researcher felt well-versed in the topic, s/he might feel comfortable with a close-ended question, providing a list of possible activities for students to choose from. If, however, the researcher is less familiar with, or confident in, the subject area, an open-ended question might be more suitable, allowing the researcher to collect needed information without the risk of excluding options that might be pertinent to students.
Time constraints: The consumption of time for both the respondent and the researcher are important. In terms of the respondent, a researcher must be realistic about the amount of time and effort a respondent is likely to invest in the completion of a questionnaire. The time and effort required of a thorough response to an open-ended question can discourage response rates on questionnaires. For the researcher, the time required to process the results of the questionnaire is an important consideration. Whereas a close-ended question provides immediate results, an open-ended question can require a significant investment of time and energy in order to transform the raw data into a form the researcher can utilize.
Level of detail desired: While convenient from a time perspective, a single close-ended question is limited in the amount of information it can gather for the researcher. Building on the example of habits of college students used above, a single closed-ended question can tell a researcher how a college student spends their time; it cannot tell the researcher why the student chooses to spend their time in the manner they indicate. Collecting more detailed information using close-ended questions would require a series of questions focused on a single topic. A single open-ended question, on the other hand, has the ability to gather information about both the how and the why simultaneously, providing more detail in a way that a single closed-ended question cannot.
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