Closed-ended questions limit respondents' answers to the survey. The participants are allowed to choose from either a pre-existing set of dichotomous answers, such as yes/no, true/false, or multiple choice with an option for "other" to be filled in, or ranking-scale response options. For example, a closed-ended question might ask for a respondent's religion, giving several religion categories (i.e., Catholic, Protestant, Buddhist, Muslim, etc.) and an "other" option.

The most common of the ranking-scale questions is called the Likert scale question. This kind of question asks the respondents to look at a statement (such as "The most important education issue facing our nation in the year 2000 is that all students in their third year of primary school should be able to read") and then "rank" this statement according to the degree to which they agree ("I strongly agree, I somewhat agree, I have no opinion, I somewhat disagree, I strongly disagree").

The advantages of closed-ended questions are:

• Closed-ended questions are more easily analysed. Every answer can be given a number or value so that a statistical interpretation can be assessed. Closed-ended questions are also better suited for computer analysis. If open-ended questions are analysed quantitatively, the qualitative information is reduced to coding and answers tend to lose some of their initial meaning. Because of the simplicity of closed-ended questions, this kind of loss is not a problem.

• Closed-ended questions can be more specific, thus more likely to communicate similar meanings. Because open-ended questions allow respondents to use their own words, it is difficult to compare the meanings of the responses.

• In large-scale surveys, closed-ended questions take less time from the interviewer, the participant and the researcher, and so they are a less expensive survey method. Generally, the response rate is higher with surveys that use closed-ended question than with those that use open-ended questions.

A limitation of closed-ended questions is the assumption that the researcher knows enough about the phenomenon being studied and about the respondents' perceptions to be able to build an appropriate and sensitive set of categories. If that is not true, the responses might be grouped into inappropriate categories or concepts. When using closed-ended questions, the researcher might first have an exploratory survey during which a small sample is asked open-ended questions. The answers obtained can be used to form categories and/or check the researcher's assumptions.

Open-ended questions do not give respondents answers to choose from, but rather are phrased so that the respondents are encouraged to explain their answers and reactions to the question with a sentence, a paragraph, or even a page or more, depending on the survey. If you wish to find information on the same topic as asked above (the future of elementary education), but would like to find out what respondents would come up with on their own, you might choose an open-ended question like "What do you think is the most important educational issue facing our nation in the year 2000?" rather than use the Likert scale question. Or, if you would like to focus on reading as the topic, but would still not like to limit the participants' responses, you might pose the question this way: "Do you think that the most important issue facing education is literacy? Explain your answer below."

The advantages of open-ended questions are:

• Open-ended questions allow respondents to include more information, including feelings, attitudes and understanding of the subject. This allows researchers to better access the respondents' true feelings on an issue. Closed-ended questions, because of the simplicity and limit of the answers, may not offer the respondents choices that actually reflect their real feelings. Closed-ended questions also do not allow the respondents to explain that they do not understand the question or do not have an opinion on the issue.

• Open-ended questions cut down on two types of response error: respondents are not likely to forget the answers they have to choose from if they are given the chance to respond freely; and open-ended questions simply do not allow respondents to disregard reading the questions and just "fill in" the survey with all the same answers (such as filling in the "no" box on every question).

• Because they can elicit extra information from the respondent, such as demographic information (current employment, age, gender, etc.), surveys that use open-ended questions can be used more readily for secondary analysis by other researchers than can surveys that do not provide contextual information about the survey population.

• Research has shown that open-ended questions are better for eliciting sensitive information, such as information about sexual assault or drug usage, than closed-ended questions.

Note: Keep in mind that you do not have to use closed-ended or open-ended questions exclusively. Many researchers use a combination of closed and open questions; often researchers use closed-ended questions in the beginning of their survey, then allow for more expansive answers once the respondent has some background on the issue and is "warmed-up."

1. This definition is modified from Types of Questions (accessed 28 December 2006).