The Blue Bird Tavern now offers delivery to campus dorm rooms. They claim that the delivery time of their food is normally distributed with a mean of 30 minutes and a standard deviation of 10 minutes. Twenty-five of your friends order their food. The average delivery time is 33 minutes. Do you have reason to disbelieve their claim? Use statistical procedures to answer this question. Identify the null hypothesis and use your statistics to explain why you would or would not reject the null hypothesis.
What will be an ideal response?
1) Std. error of mean = 10/square root of 25 = 10/5 = 2
2) Standard score = (33?30)/2 = 3/2 = 1.5
3) Two-tailed Z score is 0.13361
4) Null = delivery time is 30 minutes
5) Do not reject the null
When the null is true, the probability of observing a Z score greater than 1.5 or less than ?1.5 is 13.36 percent
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