Problem 1:

A trucking firm suspects that the mean life of a certain tire it uses is less than the advertised 45,000 miles.To check the claim, the firm randomly selects and tests 22 of these tires and gets a mean lifetime of 44,350 miles with standard deviation of 1200 miles.

a) The sample mean is 44,350.Before doing any work, what is gut feeling about the chances of the population mean being less than or equal to 45,000?Do you think that the sample mean of 44,350 is low enough and provides enough evidence?

b) At = 0.01, test the advertisement's claim.

c) Complete the hypothesis test and compare with your guess in part a.

Problem 2:

The pH of blood for normal healthy adults is generally accepted to be = 7.4.A new drug being tested is thought to decrease the pH to unhealthy low levels. A random sample of 36 patients took the drug over a 5-month period.Blood tests showed that the sample mean was 6.7 with a sample standard deviation of 1.9.Using = 0.01, test the claim that the drug has lowered the mean pH level.

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