Testing a Manufacturer's MPG Claim

Companies often develop and test hypotheses about their products. For example, car manufacturers will test their cars to determine fuel efficiency and miles per gallon. To ensure that products are safe and that they perform as advertised, regulatory and consumer protection groups also test companies' claims.

You are working at a firm that conducts independent testing for heavy industry. Recently, an automobile manufacturer has been in the news for complaints about the highway gas mileage of their latest model minivan. You receive a contract from a consumer action group to test and write a report on the company's claim that its minivans get 28 miles per gallon on the highway. The car company agrees to allow you to select randomly 35 low-mileage fleet minivans to test their highway mileage. Your test results gave you the following data:

29.7	24.5	27.1	29.8	29.2	27.0	27.8	24.1	29.3
25.9	26.2	24.5	32.8	26.8	27.8	24.0	23.6	29.2
26.5	27.7	27.1	23.7	24.1	27.2	25.9	26.7	27.8
27.3	27.6	22.8	25.3	26.6	26.4	27.1	26.1

Part 2: Hypothesis Testing: Two-Tail Test and One-Tail Test

Calculating a Two-Tail Test

List the null and alternative hypotheses for the two-tail test for the mean. Calculate the observed value of the test statistic and the associated p-value. Include your calculations. If your calculations are submitted separately, make note of where they can be found.

Interpreting the Two-Tail Test