The cost of wearing out your welcome is almost always high. You're asking people to give you one of their more precious possessions-their time.
If they feel that you're asking for too much, they may either stop in midstream and walk away or begin to answer quickly and with little or no thought, which is an ugly compromise between feeling obligated to complete the questionnaire and not wanting to give it any more time and effort.
Accordingly, the time it takes to complete a questionnaire should always be reasonable. A key determinant is the respondents' level of involvement in the category.
For example, you can probably get away with a longer questionnaire when you're interviewing people who ride motorcycles and asking questions about Harley Davidsons than you can when you're asking people about toothpaste. Another key determinant is how easy, or difficult, it is to get through the questionnaire.
If there are no bumps in the road, no thorny patches, nothing to annoy or frustrate respondents, then a 15-minute questionnaire should be just fi ne. However, if there are questions that are less than clear, questions that involve rating and raking an overly long list of attributes, repetitive questions, and questions that don't make sense, then 15 minutes is going to seem like forever and respondents will react accordingly.1
Question
1. Is there a problem with specifying the research objectives after the questionnaire has been designed? Why?
2. Why is questionnaire length an important issue in questionnaire design?