Question

An investigator compares the durability of two different compounds used in the manufacture of a certain automobile brake lining. A sample of 127 brakes using Compound 1 yields an average brake life of 42,814 miles. A sample of 163 brakes using Compound 2 yields an average brake life of 37,197 miles. Assume that the population standard deviation for Compound 1 is 1819 miles, while the population standard deviation for Compound 2 is 1401 miles. Determine the 98% confidence interval for the true difference between average lifetimes for brakes using Compound 1 and brakes using Compound 2.

Step 1 of 3 is Point estimate so 42,814 - 37,197 = 5,617

Step 2 of 3 :  

Calculate the margin of error of a confidence interval for the difference between the two population means. Round your answer to six decimal places.

Step 3 of 3:

Construct the 98% confidence interval. Round your answers to the nearest whole number. (lower and upper endpoint)

Answer 1

The statistical software output for this problem is:

Hence,

Step - 1: Point estimate = 5617

Step - 2: Margin of error = (6071.055 - 5162.945)/2 = 453.987058

Step - 3: Lower endpoint = 5163

Upper endpoint = 6071