Question

The length of human pregnancies from conception to birth varies according to a distribution that is approximately Normal with mean 266 days and standard deviation 16 days. About 99.7% of all pregnancies last between what interval?________ and _________days

Answer 1

218 and 314 days

Explanation:

The Empirical Rule states that, for a normally distributed random variable:

68% of the measures are within 1 standard deviation of the mean.

95% of the measures are within 2 standard deviation of the mean.

99.7% of the measures are within 3 standard deviations of the mean.

In this problem, we have that:

Mean = 266

Standard deviation = 16

About 99.7% of all pregnancies last between what interval?

Within 3 standard deviations of the mean. So

266 - 3*16 = 218 days

266 + 3*16 = 314 days

218 and 314 days