TABLE 9-3
An appliance manufacturer claims to have developed a compact microwave oven that consumes a mean of no more than 250 W. From previous studies, it is believed that power consumption for microwave ovens is normally distributed with a population standard deviation of 15 W. A consumer group has decided to try to discover if the claim appears true. They take a sample of 20 microwave ovens and find that they consume a mean of 257.3 W.
-Referring to Table 9-3, the consumer group can conclude that there is enough evidence that the manufacturer's claim is not true when allowing for a 5% probability of committing a Type I error.

Question

Quizplus · Accepted Answer

The consumer group can perform a hypothesis test with the null hypothesis that the mean power consumption is 250 W. Using the sample mean of 257.3 W, sample size of 20, and population standard deviation of 15 W, they can calculate the z-score and compare it to the critical value for a 5% significance level. If the z-score exceeds the critical value, they can reject the null hypothesis, indicating enough evidence against the manufacturer's claim.

TABLE 9-3 An Appliance Manufacturer Claims to Have Developed a Compact Microwave