The gestation time for humans has a mean of 266 days and a standard deviation of 25 days. If 100 women are randomly selected, find the probability that they have a mean pregnancy between 266 days and 268 days.

Suppose that the mean gestation time for the 100 women selected at random was  =265 days. Suppose the researchers take another sample of 100 women. Would you expect the mean and the standard deviation of this new sample to exactly the same (i.e.   =265 days)?

Suppose the researchers were able to collect gestation time for an additional 100 women (total sample size is now n=200).

How would doubling the sample size affect the standard error (SE) of the mean? 

SE would decrease.

SE would increase.

SE would stay the same.

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