The average drying time of a manufacturer’s paint is 20 minutes. Investigating the effectiveness of a modification in the chemical composition of her paint, the manufacturer wants to test the null hypothesis µ = 20 minutes against a suitable alternative, where µ is the average drying time of the modified paint.
(a) What alternative hypothesis should the manufacturer use if she does not want to make the modification in the chemical composition of the paint unless it decreases the drying time?
(b) What alternative hypothesis should the manufacturer use if the new process is actually cheaper and she wants to make the modification unless it increases the drying time of the paint?