A company is studying the average manufacturing time of the same product two years ago (denoted Year 1) and last year (denoted Year 2). Independent random samples have been selected from each year and the results (in minutes) are shown below.

Year 1 Year 2
Sample Size 20 25
Sample Mean 14 12

Sample standard deviation 6 9

1. a) Use the 10% level of significance and the p-value approach to determine if the average manufacturing time of the product decreased over time.

1. b) Construct a 99% confidence interval estimate of the difference between the average manufacturing time in Year 1 and the average manufacturing time in Year 2.