Multiple-choice questions on surveys present several challenges (See my post of Dec. 20, 2005 on several methodological issues.). Because surveys use them all the time, it is worth noting one more criteria to keep in mind for multiple-choice inquiries.
One egregious error is for a survey question to give several choices, some of which overlap with others, while at the same time to omit reasonable, obvious choices (See my post of May 10, 2006 for some sloppiness from a Canadian survey; and March 31, 2007 about obstacles to alignment with clients.).
The ultimate goal for a surveyor is to provide all the choices that respondents might want to select and yet to avoid overlap between any of them. Consulting firms refer to this two-pronged test as MECE (pronounced Me Sea) – Mutually Exclusive and Collectively Exhaustive. It is an unattainable goal but it is a guideline to improve the quality of surveys and the conclusions drawn from them.