Determining the ideal length of a questionnaire can be a difficult process. Oftentimes the process involves a reassessment of the purpose or focus of a questionnaire, with an eye toward eliminating all questions that are not absolutely necessary. Before removing question items, however, the factors listed below are worth considering.
Characteristics of the sample population: In terms of willingness to complete a questionnaire, not all sample populations are created equal. Some populations, like those that have just participated in an experience (such as a college course), are inherently more motivated to complete a questionnaire that deals with the experience in question. Other populations, however, can be difficult to motivate. Generally speaking, the more motivated the population, the more likely they are to complete questionnaires of greater length.
Question types utilized: The length of a questionnaire should be measured not only in terms of the number of questions, but also in terms of the time it takes to formulate a response to those questions. As a result, the type of questions utilized in a questionnaire can have an important impact on the “length” of a questionnaire. While many Likert-scale type questions require only a minute or two to complete, open-ended questions can take considerably more time. Moreover, open-ended questions require the respondent to do more than just think about how they feel with regard to the question prompt – they must also devote time to crafting a coherent response. As a general rule, there should be an inverse relationship in a questionnaire between the number of open-ended questions utilized and the total number of questions featured in the questionnaire.
Questionnaire format: The different formats available to a researcher often come with expectations about time required on the part of respondents. Focus groups or interviews, for example, often take at least 30 minutes to complete. Questionnaires administered over the telephone, however, usually take considerably less time. Questionnaires administered online are less predictable. While shorter is often better, the ability of the respondent to complete the questionnaire at their convenience allows for greater flexibility. The length of paper mailings is often dictated more by the increased cost of postage associated with heavier mailings than a concern over the time it will take respondents to complete the questionnaire.
Further Reading
Neuman, W. L. (2007). Basics of social research: Qualitative and quantitative approaches (2nd ed.). Boston, MA: Allyn and Bacon.
Suskie, L.A. (1996). Questionnaire survey research: What works (2nd ed.). Tallahassee, FL: Association for Institutional Research