Welcome to part 4 of the response process model: mapping.
Encode –> Comprehend –> Retrieve –> Map –> Report
A respondent could understand your question (and remember the answer), but not be able to place their response in any of the categories available to them.
My favorite example of mapping difficulties came when I worked administering a survey to drug addicts about their use. For each drug they had used in the previous week, I asked them to estimate the amount. The answer categories in the survey were expressed in grams (less than a quarter of a gram, between a quarter and half a gram, etc). Yet, most people gave answers like “about $50 worth” or “hundreds of dollars worth.” Since they didn’t know the weight, and I didn’t know the street value of cocaine, we usually ended up at an impasse—and the researchers ended up without usable data.
A less dramatic but very common mistake I see is:
How old are you?
- Under 18
- Over 35
A respondent may be certain that she is 35 years old, but not certain how to answer this question. None of the answer categories “map” to this response. A good rule of thumb is that everyone needs to fit in one and only one category.
When it comes to avoiding mapping difficulties, pre-testing questions is highly recommended; it will quickly become apparent if respondents can’t navigate the answer categories.