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. According to the empirical rule, approximately 95% of all pregnancies last between what?

Answer 1

The empirical rule says about 95% of any normal distribution lies within two standard deviations of the mean. This means in this case 95% of pregnancies last between

$266-2\times16=234$

and

$266+2\times16=298$

days.