Normally distributed

Question

The length of a particular aniamals pregnancied are approximately normally distributed with mean =250 days and standard deviation 16 days. What proportion of pregnancies lasts mare than 262 days?

Answer 1

Calculate the z statistic:

z = (X - µ) / σ

= (262 - 250) / 16

= 0.75 <= this is the Z score, which is the # of standard deviations away from the mean

From a table of standard normal probabilities, Pr(Z > 0.75) = 1 - 0.7734 = 0.2266 = 22.66%