How Should the Researcher Handle “Don’t Know” Responses?
After all, it is assumed that a “DK/NO” only attracts those respondents that truly do not know the answer to the question or do not have an opinion on the surveyed topic. Yet, you can never be 100% certain that an opinionated respondent will not opt for the “DK/NO” option. As a result, the initial assumptions do not hold. That is why it is argued that you should not automatically presume that every time a respondent chooses for a “DK/NO”, (s)he cannot report a meaningful response.
As a matter of fact, most of the existing imputation procedures are not appropriate to handle dk responses (Feick, 2005, e.g.) and some alternatives have been proposed in the literature (Feick, 2005; Kroh, 2006). Following another approach, dk could be treated as one of the possible response categories. However, the addition of the dk category to the ordered ratings imposes a nominal scaling level to the random variable generating responses and this prevents the use of the statistical methods usually employed to model ratings, as they are mostly conceived for ordinal data.
Rubin, D.B., Stern, H.S., Vehovarc, V., 1995. Handling “don’t know” survey responses: The case of the slovenian plebiscite. J Am Stat Assoc 90, 822–828
Feick, L.F., 2005. Latent class analysis of survey questions that include don’t know responses. Public Opin Quart 53, 525–547.