According to a recent National Health Statistics Reports the

According to a recent National Health Statistics Reports, the weight of the male babies less than 2 months old in the US is normally distributed with a mean of 11.5 pounds and standard deviation of 2.7 pounds. A. What percent of babies weigh more than 13 pounds? B. What percent of babies weigh less than 15 pounds? C. What percent of babies weigh between 10& 14 pounds? D. Is it unusual for a baby boy to weigh more than 17 pounds?

Solution

A. P(X>13) =1-0.71074=0.2892

using NORM.DIST function in excel.

hence 28.92% of babies weigh more than 13 pounds.

B.P(X<15)=0.9025

So 90.25% of babies weigh less than 15 pounds.

C. P(10<x<14)=0.8227-0.2892=0.5115 so 51.15% of babies weigh between 10 and 14 pounds.

D. 99% of values fall between (3.4,19.6) i.e mean-3sd,mean+3sd

D.