Question

7) The Speedy Oil Change Company advertises that the average mean time it takes to change a customer's oil is 30 minutes. After receiving complaints from dissatisfied customers, the management at Speedy Oil Change headquarters hired a researcher to investigate the complaints to determine if the oil change took significantly longer than 30 MAT 102 DAH Test# 3 Form A NAME 8 minutes. The researcher randomly investigates 16 oil changing jobs and computes the sample mean time to change a customer's oil is 32.8 minutes with a sample standard deviation of 6.9 minutes. Based on this sample result, can the researcher conclude that Speed Oil Change Company's claim is too low at α = 5 %? I. State the hypotheses (in words & symbols): Ho: Ha: I Determine the model to test Ho a) Can you use a normal distribution for the Sampling Distribution model to perform this test? Please explain. If not, then what distribution could you use?

Answer 1

1.let ù be the average mean time taken to change a customers oil. So null hypothesis is ù=30

As it takes that much time according to the problem.

And alternative hypotheis is ù> 30 as accroding to the customers complaints the management wants to study if the oil change time takes average time more than 30 minutes or not.

2. As the sample size is not large enough we cannot make normal approximation hence cannot use normal distribution for the sampling distribution.