Thread: Statistics

I need help starting these...


1. Suppose that you want to test the claim that the mean weight of male harbor seals is 300 pounds. You collect a sample of 90 seals and find that the mean weight in the sample is 308 pounds. Using a level of significance α = 0.05 and a standard deviation of 23, test the null hypothesis H0: µ=300.


2. OilChange, Inc., an automotive tune-up shop, advertises that its personnel can, on average, carry out an oil change in 10 minutes or less. The Better Business Bureau received complaints from customers that it actually takes considerably longer to carry out an oil change at OilChange. To check the company’s claim, the Better Business Bureau had the oil changed on 50 unmarked cars. The mean time it took for an oil change was 10.5 minutes, with a sample standard deviation of 1 minute.


a. Since 10.5 minutes is greater than the claimed value of 10 minutes, explain why we even need to carry out a hypothesis test.


b. At the level of significance of α = 0.01, carry out a hypothesis test to test OilChange’s claim.

1. Suppose that you want to test the claim that the mean weight of male harbor seals is 300 pounds. You collect a sample of 90 seals and find that the mean weight in the sample is 308 pounds. Using a level of significance α = 0.05 and a standard deviation of 23, test the null hypothesis H0: µ=300.

Please do not double post. Answered in another post.

2. OilChange, Inc., an automotive tune-up shop, advertises that its personnel can, on average, carry out an oil change in 10 minutes or less. The Better Business Bureau received complaints from customers that it actually takes considerably longer to carry out an oil change at OilChange. To check the company’s claim, the Better Business Bureau had the oil changed on 50 unmarked cars. The mean time it took for an oil change was 10.5 minutes, with a sample standard deviation of 1 minute.

Since the customers believe it is longer than the garage says, we have a right tail test.




b. At the level of significance of α = 0.01, carry out a hypothesis test to test OilChange’s claim.

Now, proceed as in the other post. You have all the data needed.