One of the most common mistakes I see in questionnaire design is the problem of overlapping scales. Take this question for example:
Which of the following includes your age?
O 18-25
O 25-35
O 35-45
O 45-55
O 55+
If the respondent is 35 years old, which response option should she select: “25-35″ or “35-45″? This seems like common sense, yet I see this mistake made time and time again.
There are several significant problems caused by overlapping scales. First, respondents may conclude that the survey sponsor is inept or unsophisticated. Second, this type of error can lead to above-average rates of survey abandonment (when respondents exit the survey before completing it). Finally, and perhaps most importantly, it can significantly skew the survey data.
Here are two bits of advice to make sure you don’t fall into the trap of this common mistake:
- Always make sure that single-selection response options are mutually exclusive
- Always pretest the survey
The bottom line: the problem with overlapping scales is one of the most common mistakes of questionnaire design. Ensuring that your response options are mutually exclusive will not only produce more reliable data, but will also provide a better experience for your respondents .
