1. The Excel file Mortgage Rates contains time‐series data on rates of three dif

1. The Excel file Mortgage Rates contains time‐series data on rates of three different mortgage instruments. Assuming that the data are stationary, construct a 95% confidence interval for the mean difference between the 30‐year and 15‐year fixed rate mortgage rates. Based on this confidence interval, would you conclude that there is a difference in the mean rates? 2. The Excel file Student Grades contains data on midterm and final exam grades in one section of a large statistics course. Construct a 95% confidence interval for the mean difference in grades between the midterm and final exams.

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