Question: Rural roads with little or no evening lighting use reflective paint to mark the lanes on highways. It is suspected that the currently used paint does not maintain its reflectivity over long periods of time. Three new types of reflective paint are now available and a study is initiated to compare all four types of paint.

(a) How many populations are involved in the study?

(b) What is considered a treatment in this study?

(c) Letting µ₁ denote the mean time the currently used paint maintains its reflectivity, and µ₂, µ₃, and µ₄ denote the corresponding means for the three new types of paint, write the control versus treatment contrasts.