When is two not better than one? In survey design two is certainly not better than one. In this case it refers to the use of double-barreled questions. Those with little research training often do not realize they are combining two distinct elements into one question. The best practice is to separate out each element into its own question.
For example:
In your most recent visit to Abby’s Attic were you satisfied with your purchase and the amount of time it took to complete your shopping trip?
What we are looking at in this case is two elements: 1) purchase satisfaction and 2) expectations regarding length of shopping trip.
The next is an employee survey example. It was taken from a post-sales training event survey.
After the Acme presentation, do you feel you better understand their 2013 initiatives and how to better engage with their field reps?
This would be better served by splitting it into two questions, perhaps using a matrix format.
Regarding the Acme presentation…
- Do you feel you better understand their 2013 initiatives? Yes/No
- Are you better prepared to engage their field reps? Yes/No
Alternatively it could be re-phrased into a Likert Scale format with the focus clearly on the respondent.
- I fully understand the 2013 Acme initiatives.
- I am better prepared to engage Acme field representatives.
The rise of the do-it-yourself movement in consumer and B2B market research has lead to some dubious questionnaire designs. One of the cardinal sins in survey development is to merge two concepts into a single question. If you find yourself using “and” in your phrasing then you may just be staring down a double-barreled question.