Womens weights are normally distributed with a mean given by

Women\'s weights are normally distributed with a mean given by D4 which separates the bottom 40% from the top 60%. Sigma = 29 ib . Find the fourth decile Mu = 143 lb and a standard deviation given by

Solution

P(X<x) = 0.4

-- > P((X-mean)/s <(x-143)/29) = 0.4

--> P(Z<(x-143)/29) =0.4

--> (x-143)/29 = -0.25 (from standard normal table)

So x= 143-0.25*29 =135.75