In Exercise 13.1 the design may have a major weakness from a practical point of view. Notice the group of multiparous mothers under 18 years of age. Without regard to the data, would you expect this...

In Exercise 13.1 the design may have a major weakness from a practical point of view. Notice the group of multiparous mothers under 18 years of age. Without regard to the data, would you expect this group to lie on the same continuum as the others?

Refer to Exercise 13.1. It seems obvious that the sample sizes do not reflect the relative frequency of age and parity characteristics in the population. Under what conditions would this be a relevant consideration, and under what conditions would it not be?