Which of the following is a source of the sort of systematic measurement error attributable to errors/problems with the questionnaire itself?
a. A sample design error on the part of the researcher results from a misdiagnosis of the desired population of interest.
b. Deliberate falsification on the part of the respondent (he/she deliberately answers in a way that is false).
c. The response options are either misleading or inappropriate, which causes confusion and consistently incorrect responses from those completing the survey (with the error usually occurring in the same direction).
d. During the data collection phase, the researcher vastly oversamples a subset of the population of interest.