"Don't Know": Item Ambiguity or Respondent Uncertainty?

Abstract

What to do with “Don't Know” responses in survey data is dependent upon a prior understanding of their causes. A proximity analysis of the “Don't Know” responses alone yields the same scale as does a scalogram analysis of the definite responses alone indicating response uncertainty as one source of the response. The quality of the scales is improved by eliminating ambiguous items, indicating stimulus ambiguity as another source. The data used are responses to items on attitude toward abortion obtained in an island-wide survey of Taiwan.