Question

# An investigator compares the durability of two different compounds used in the manufacture of a certain...

An investigator compares the durability of two different compounds used in the manufacture of a certain automobile brake lining. A sample of 259 brakes using Compound 1 yields an average brake life of 31,495 miles. A sample of 297 brakes using Compound 2 yields an average brake life of 41,15241,152 miles. Assume that the population standard deviation for Compound 1 is 1446 miles, while the population standard deviation for Compound 2 is 4520 miles. Determine the 99% confidence interval for the true difference between average lifetimes for brakes using Compound 1 and brakes using Compound 2.

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 99% confidence interval. Round your answers to the nearest whole number. (lower and upper endpoint)

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