Answer:
To reduce bias when estimating mean commuting time
Step-by-step explanation:
Given that the selection of adults is based on the three strata found in the region; urban, suburban, and rural areas where the population and proportion of adults commuting to work is progressively decreasing, using a uniform number or sample size will not increase sample error as there are more commuters in the urban areas than in the suburban or rural areas, likewise, there are more commuters in the suburban area than in the rural areas, and as such the proportion of those sampled in the urban areas should be more than those surveyed in the suburban while those surveyed in the suburban areas should be more than those surveyed in the rural areas to reduce bias when estimating the mean as there will be more general representation.