12.50. True or false? Suppose that forsubjects aged under 50, there is little difference in mean annual medical expenses forsmokers and nonsmokcrs, but forsubjects aged over 50 there is a large difference. Then there is no interaction between smoking status and age in their effects on annual medical expenses.

Select the correct response(s) in Exercises 12.51-12.54.

(More than one response may he correct.)