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 540HP . Nine engines are randomly selected for horsepower testing. The sample has an average maximum HP of 570 with a standard deviation of 30HP. Assume the population is normally distributed. Calculate a confidence interval for the average maximum HP for the experimental engine. Use a significance level of α=0.01.

Answer 1

The 99% of a confidence interval for the average maximum HP for the experimental engine.

(536.46, 603.54)

Explanation:

Step:-1

Given that the mean of the Population = 540HP

Given that the size of the sample 'n' = 9

Given that the mean of the sample = 570HP

Given that the sample standard deviation = 30HP

Step(ii):-

Degrees of freedom = n-1 =9-1 =8

t₀.₀₀₅ = 3.3554

The 99% of a confidence interval for the average maximum HP for the experimental engine.

`(x^(-) - t_{(0.01)/(2) ,8} (S.D)/(√(n) ) ,x^(2) + t_{(0.01)/(2),8 } (S.D)/(√(n) ) )`

`(570-3.354(30)/(√(9) ) , 570+3.354(30)/(√(9) ) )`

(570 - 33.54 , 570+33.54)

(536.46 , 603.54)

Final answer :-

The 99% of a confidence interval for the average maximum HP for the experimental engine.

(536.46, 603.54)