The 98% confidence interval for the mean repair cost for the dryers is (83.4161, 103.3039).
Step-by-step explanation:
We have a small sample size n = 25, and s = 19.95. The confidence interval is given by where is the th quantile of the t distribution with n - 1 = 25 - 1 = 24 degrees of freedom. As we want the 98% confidence interval, we have that and the confidence interval is where is the 1st quantile of the t distribution with 24 df, i.e., . Then, we have and the 98% confidence interval is given by (83.4161, 103.3039).