When do you ask? When observations are taken over time, it is important to check for patterns that may be important for the interpretation of the data. In Section 1.1 we learned to use a time plot for this purpose. Describe and discuss a sample survey question where you would expect to have variation over time for the following situations:

(a) Data are taken at each hour of the day from 8 A.M. to 6 P.M.

(b) Date are taken on each of the 7 days of the week.

(c) Data are taken during each of the 12 months of the year.