A survey asks respondents their age and offers the categories 20-30, 30-40, 40-50 and 50+. Which key rule for closed-ended questionnaire items does this break?
Correct answer D. Mutually exclusive
Explanation
Response categories must be mutually exclusive so that each answer fits only one option; here a person aged 30 or 40 could tick two boxes because the ranges overlap.
Answer checked How we write and check questions
Discussion