What proportion of pregnancies last fewer than 262 days? P(X < 262 days)

Question

The lengths of pregnancies in a small rural village are normally distributed with a mean of 260 days and a standard deviation of 16 days. A distribution of values is normal with a mean of 260 and a standard deviation of 16.

What proportion of pregnancies last fewer than 262 days?

P(X < 262 days) =

Answer 1

P(x < 262) = P(z < (262 - mean)/SD) = P(z < (262 - 260)/2) = P(z < 1) = 0.8413