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Wetzelhütter, Daniela. 2020. “Scale-Sensitive Response Behavior!?  Consequences of Offering versus Omitting a ‘Don’t Know’ Option and/or a Middle Category.” Survey Practice 13 (1). https://doi.org/10.29115/SP-2020-0012.
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  • Figure 1: Literature recommendation for omitting vs. providing a DK-O or MC (if certain conditions apply)
  • Figure 2: Typification of answer strategies based on available scale format
  • Table 1: Group affiliation based on the availability of a MC and/or a DK-O (n=1,282)
  • Figure 3: Frequency distribution, summarized per set of items (A, B, C), differentiated by group affiliation (in percent)
  • Table 2: Average number of MCs and DK-Os chosen considering the scale format (n=1,282)
  • Figure 4: Proportion of MCs chosen, per set of items (A, B, C), depending on the availability of a DK-O, differentiated by voters vs. nonvoters (in percent)
  • Figure 5: Proportion of DK-Os chosen, per set of items (A, B, C), depending on the availability of a MC, differentiated by voters vs. nonvoters (in percent)
  • Table 3: Frequency distribution, per set of items (A, B, C) (excluding “don’t know” and “moderate” responses)
  • Figure A-1 Answer categories tagged with face emojis
  • Figure A-2: Answer categories tagged with radio buttons


The effect of a “don’t know” option (DK-O) and of a “middle category” (MC) on the survey response has been frequently examined. While researchers agree on some points, they disagree on how these options should be interpreted. For instance, a DK-O or MC may not necessarily be chosen due to a lack of a neutral/moderate opinion. This article addresses the consequences of offering versus omitting a MC or/and a DK-O. Data were collected by means of an online survey dealing with student participation (n=1,282). The results showed respondents who choose a DK-O may not have a neutral opinion. Conversely, respondents who choose a MC may not necessarily be undecided.

Accepted: September 02, 2020 EDT


Extracts of questions and given answer categories

Figure A-1
Figure A-2:Answer categories tagged with radio buttons

Note: Translated, the question reads as follows: Figure A-1: “How satisfied are you …”, “… with the study related information on the student unions (ÖH) homepage?”, “…the work/the engagement of student representation of the study program?”, “…the services of the student union (ÖH) concerning the everyday life of the students?”; Figure A-2: “How satisfied are you with how the student union (ÖH) has stood up for the following topics so far?”. The listed topics are “Remission of tuition fees,” “Definition of admission criteria for studying,” “Library: longer opening hours,” and “Library: book orders.” The end points of the regular answer categories of all three sets of items were labeled “very satisfied” and “not satisfied at all.” The label of the sixth option was “don’t know.” The answer categories were tagged either with face emojis or with buttons. The DK-O was made noticeable as an additional, irregular category in order to ensure that the conceptual midpoint was visible, independently of the presence of a DK-O.

  1. https://www.oeh.univie.ac.at/wahlkommission