A random sample is selected from a
normal population. The population mean is ?=60 and the population standard
deviation is ?=15. After a treatment is given to the members of the sample, the
sample mean is M=65. The sample size is n=25.

The hypothesis test:

H0: ?=60

H1: ?= <>60

?=0.05

Give reason why or why not the
sample mean is sufficient to conclude that the treatment has a significant
effect.