Chapter 6, Problem 38RE

To determine

To calculate: the percentage of pregnancies last between 250 days and 280 days.

Answer to Problem 38RE

The percentage pregnancies last between 250 days and 280 days is 67.31%.

Explanation of Solution

Given information: Lengths of human pregnancies are normally distributed with mean

268 days and standard deviation 15 days.

Calculation:

The pregnancies last between 250 days and 280 days:

  $={\displaystyle \underset{250}{\overset{280}{\int }}\frac{1}{15\sqrt{2\pi }}}{e}^{-\frac{{(x-268)}^2}{2\times {15}^2}}=0.6731$

So, the percentage pregnancies last between 250 days and 280 days is 67.31%.