My wife, who studied cognitive science at MIT, says that studies have shown that people are best able to give consistent responses when they're given a choice of 1-7. 1-7 allows people to give an answer thusly:
1: As bad as possible
2: Pretty bad, but not as bad as it can get
3: Slightly bad
4: Medium
5: Pretty good
6: Quite good, but not as good as it can get
7: As good as it can get
I've had good results with this scale myself.
If you give only 5 choices, you can't distinguish "slightly bad" from "quite bad but not as bad as it can get". So it's really not enough choices. On the other hand, if you have 10 choices, in most cases you can't qualitatively distinguish between 10 individual states. For example, if you're trying to rate your mood on a scale of 1-10, what is the qualitative difference between feeling "2" and feeling "3"? It's too fine a distinction. But the difference between "2" and "3" on a scale of 7 (see above) is easier to get ahold of.
|