If your population is 10,000, you'll need to survey 378 people. If its 5,000, survey 357. Now you've got your sample of about 360 people. Your decision about the method of sampling will probably be influenced by your budget and your timetable. Mail is low cost, but slow, and often doesn't have a good response rate without incentives.
Telephone surveys have a moderate cost, and they are fast.
Of course, there are other ways to elicit quantitative information besides surveys, such as experiments and observation, but we'll stick with this most popular approach. That's why most surveys either provide the answers or furnish the scale on which to rate specific responses. They're easy to administer, quick to score, and easy to understand. But they do reduce the richness and variability of the responses. Some surveys use a combination of both types of questions.