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Bolcic-Jankovic, Dragana, Eric G. Campbell, Jessica L. LeBlanc, Manan M. Nayak, and Ilana M. Braun. 2021. “Using ‘Don’t Know’ Responses in a Survey of Oncologists Regarding Medicinal Cannabis.” Survey Practice 14 (1). https://doi.org/10.29115/SP-2020-0016.
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  • Figure 1
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  • Table 1: Respondents’ characteristics.
  • Table 2: DK responses by respondents’ characteristics.
  • Table 3: Logistic regression results for control variables on DK responses.
  • Table 3 (continued): Logistic regression results for control variables on DK responses.


Objective: To evaluate whether “Don’t Know” (DK) responses conveyed meaningful information when provided by oncologists in a national survey on medicinal cannabis (MC).

Study Setting: This study is a secondary analysis of national survey data (n=237) collected between November 2016 and January 2017.

Methods: The national survey asked oncologists about views regarding MC’s risks/benefits, and whether they had sufficient knowledge to make MC recommendations clinically. Cognitive testing of the survey instrument (n=5) suggested that physicians did not always feel that they possessed adequate MC knowledge in all domains, so DKs were added to six of 27 survey items. (Three items were batteries of questions while three were single questions.) We constructed bar graphs for the sum of DK responses in each battery and for the sum of all DK responses in the survey. Mann-Whitney tests compared medians for all DK responses within Yes/No responses to the sufficient knowledge question.

Principal Findings: Statistically significant associations between DK responses and the sufficient knowledge question indicate that DK answers improved data quality by providing all respondents with an answer category that they feel fits their “true” answer. Associations between DK answers and other background variables such as respondents’ age, sex, and race are also discussed. The logistic regressions found that possessing sufficient knowledge was the only variable significant across six of the nine regressions, and the direction was consistent with the bivariate findings.

Conclusion: In this study, DKs appear to be valid responses, improving data quality by providing some respondents with an answer category that best fits their “true” answer. Future surveys aiming to learn about physicians’ views regarding emerging treatments might consider including the DK response option in some items.

Accepted: December 14, 2020 EDT