[EX09-028] The addition of a new accelerator is claimed to decrease the drying time of latex paint by more than 4%. Several test samples were conducted with the following percentage decrease in drying time. 5.2 6.4 3.8 6.3 4.1 2.8 3.2 4.7 Assume that the percentage decrease in drying time is normally distributed.

a. Find the 95% confidence interval for the true mean decrease in the drying time based on this sample. (The sample mean and standard deviation were found in answering Exercise 2.181, p. 129.)

b. Did the interval estimate reached in part a result in the same conclusion as you expressed in answering part c of Exercise 2.181 for these same data?