Aregional transportation authority is interested in estimating the mean number of minutes working adults in the region spend commuting to work on a typical day. a random sample of working adults will be selected from each of three strata: urban, suburban, and rural. selected individuals will be asked the number of minutes they spend commuting to work on a typical day. why is stratification used in this situation?

a. to remove bias when estimating the proportion of working adults living in urban, suburban, and rural areas. b. to remove bias when estimating mean commuting time. c. to reduce bias when estimating mean commuting time. d. to decrease the variability in estimates of the proportion of working adults living in urban, suburban, and rural areas. e. to decrease the variability in estimates of the mean commuting time.