Interviewer and coder bias is eliminated because the interviewer is simply checking a box, circling a category, recording a number, or pressing a key. Reading response alternatives can refresh a person’s memory and provide a more realistic response. Also, because the option to expose a topic is not given to a respondent, there is no bias towards articulation. Finally, the data acquisition and encoding process is greatly simplified.
There is a difference between a precoded open question and a closed question. An open question allows the respondent to answer in a free format. The interviewer simply checks the points on the prerecorded responses as they are given. Polling is used, but a list is never read. If an answer is given that is not prerecorded, it is written word for word in the “other” column. In contrast, the closed question requires that alternatives be read or shown to the respondent.
Traditionally, the data acquisition process has separated the two-item response option from the many-item type. A two-choice question is called dichotomous, and the many-item type is often called multiple-choice or multichotomous. With the dichotomous closed question, the response categories are sometimes implicit. For example, how would you answer the following question: “Did you buy gas for your car in the last week?” Obviously, the implied choices are “Yes” or “No” regardless of whether a respondent might say, “I rented a car last week and they filled it up. Does that count?” the questions would still be classified as dichotomous and closed.
The simplest form of data acquisition is a closed question or a dichotomous choice. They are easy to administer and usually provoke a quick response. For example, limit responses to a simple “Yes” or “No”, “Agree” or “Disagree” or “Greater than” or “Less than”. Many times a neutral or “no opinion / don’t know” option is added to dichotomous questions to resolve these situations. Sometimes the interviewer will write “DK” for “Don’t know” or “NR” for “No answer” if the neutral option is omitted from the data acquisition questionnaire.
Dichotomous questions are prone to a large number of measurement errors. Because the alternatives are polarized, the wide range of possible choices between the poles is omitted. Therefore, the wording of the questions is essential to obtain accurate answers. Questions posed in a positive way can lead to answers that are the opposite of those put in a negative way. For questions that require a “Greater than” or “Less than” answer, the answer may vary. These problems can be overcome using a split voting technique. Half of the questionnaires are written with more than what is listed first and the other half with less than first. This procedure will help reduce potential bias.
Each type of closed question has unique disadvantages. For the dichotomous data acquisition form, responses often fail to communicate any intensity of respondent sentiment. In some cases, the question of intensity does not apply, as in the previous example regarding the purchase of gasoline, but cases arise in which the respondent feels very strongly about a problem but the intensity is lost in the form of acquisition dichotomous data. The closed multiple-choice question has two additional disadvantages. First, the researcher must spend time compiling the list of possible answers, second, the range of possible answers. If the list is too long, respondents may become confused or disinterested.