Answer to Question 1
a . Personal interview: involves an interviewer soliciting information from a respondent by asking prepared questions; it has a higher expected response rate but is typically expensive.
b. Telephone interview: involves soliciting information by calling people. This is usually less expensive, but it is also less personal and has a lower expected response rate.
c. Self-administered survey: this is an inexpensive method of conducting a survey which is usually mailed to a sample of people; it usually has a very low response rate.
Answer to Question 2
In an observational study, there is no attempt to control factors that might influence the variable of interest. In an experimental study, a factor (such as regular use of fitness center) is controlled by randomly selecting who is exposed to that factor, thereby reducing the influence of other factors on the variable of interest.
