Question

The average precipitation for the first 7 months of the year is 19.32 inches with a standard deviation of 2.4 inches. Assume that the average precipitation is normally distributed. What is the probability that a randomly selected year will have precipitation greater than 18 inches for the first 7 months?

Answer 1

$\mu=19.32,\sigma=2.4$

$P(X>18)=P(Z>\frac{x-\mu}{\sigma})=P(Z>\frac{18-19.32}{2.4})$

$=P(Z>-0.55)=1-P(Z<-0.55)$

$=1-0.2912$

$=0.7088$