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 600 HP. Sixteen engines are randomly selected for horsepower testing. The sample has an average maximum HP of 620 with a standard deviation of 45 HP. Calculate a 95% confidence interval for average maximum HP. Round your answer to one decimal place. (Answer: 595.5 to 644.5)

Answer 1

Answer:

The 95% confidence interval the average maximum power is (596.0 to 644.0)

Step-by-step explanation:

Average maximum of the sample = x = 620 HP

Standard Deviation = s = 45 HP

Sample size = n = 16

We have to calculate the 95% confidence interval. The value of Population standard deviation is unknown, and value of sample standard deviation is known. Therefore, we will use one sample t-test to build the confidence interval.

Degrees of freedom = df = n - 1 = 15

Critical t-value associated with 95% confidence interval and 15 degrees of freedom, as seen from t-table = $t_{\frac{\alpha}{2}}$ = 2.131

The formula to calculate the confidence interval is:

$(x-t_{\frac{\alpha}{2} } \times \frac{s}{\sqrt{n} }, x+t_{\frac{\alpha}{2} } \times \frac{s}{\sqrt{n} })$

We have all the required values. Substituting them in the above expression, we get:

$(620-2.131 \times \frac{45}{\sqrt{16} }, 620+2.131 \times \frac{45}{\sqrt{16} })\\\\ =(596.0 , 644.0)$

Thus, the 95% confidence interval the average maximum power is (596.0 to 644.0)