Humans are known to have a mean gestation period of 280 days (from last menstruation) with a

Question:

Humans are known to have a mean gestation period of 280 days (from last menstruation) with a standard deviation of about 9 days. A hospital wondered whether there was any evidence that their patients were at risk for giving birth prematurely. In a random sample of 70 women, the average gestation time was 274.3 days.

(a) Is the alternative hypothesis one- or two-sided?

(b) Test the null hypothesis at α = 0.05.

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