Question

High-power experimental engines are being developed by the Stevens Motor Company for use in its new sports coupe. The engineers have calculated the maximum horsepower for the engine to be 830⁢HP. Twenty five engines are randomly selected for horsepower testing. The sample has an average maximum HP of 880880 with a standard deviation of 55⁢HP. Assume the population is normally distributed.

Step 1 of 2 :  

Calculate a confidence interval for the average maximum HP for the experimental engine. Use a significance level of α=0.01. Round your answers to two decimal places.

Answer 1

Given : = 880, s = 55, n = 25, = 0.01

Since n < 30 and population standard deviation is unknown, the tcritical (2 tail) for = 0.01, for df = n -1 = 24, is 2.797

The Confidence Interval is given by ME, where

The Lower Limit = 880 - 30.77 = 849.23

The Upper Limit = 880 + 30.77 = 910.77

The Confidence Interval is (849.23 , 910.77)