Question Difficulty and Respondents' Cognitive Ability: The Impact on Data Quality

Older respondents lower in cognitive ability are more affected by question difficulty than older respondents higher in cognitive ability. Respondents lower in cognitive ability gave more DK responses to difficult than to easy questions, while the differences between the difficult and easy questions were not as apparent for respondents with higher cognitive abilities. This effect may result in biased survey findings because responses to difficult questions from respondents with lower cognitive ability would be underrepresented.