An appliance manufacturer claims to have developed a compact microwave oven that

Question

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 Scenario 9.3, for a test with a level of significance of 0.05, the critical value would be ____

Explanation / Answer

As we have to test the claim that the oven consumes a mean of no more than 250W, the critical value will be computed as:

P( Z > K ) = 0.05

From standard normal tables we get:

P ( Z > 1.645 ) = 0.05

Therefore 1.645 is the required critical value for this test.

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