The total cholesterol levels of a sample of men aged 35-44 are normally distribu

Question

The total cholesterol levels of a sample of men aged 35-44 are normally distributed with a mean of 208 milligrams per deciliter and a standard deviation of 37.1 milligrams per deciliter. (a) What percent of the men have a total cholesterol level less than 216 milligrams per deciliter of blood? (b) If 242 men in the 35-44 age group are randomly selected, about how many would you expect to have a total cholesterol level greater than 264 milligrams per deciliter of blood? (a) The percent of the men that have a total cholesterol level less than 216 milligrams per deciliter of blood is (Round to two decimal places as needed) (b) Of the 242 men selected, would expected to have a total cholesterol level greater than 264 milligrams per deciliter of blood (Round to the nearest integer as needed.)

Explanation / Answer

ans=

(a) P(X<216) = P((X-mean)/s <(216-208)/37.1)
         = P(Z<1.42) =0.9207 (From standard normal table)
             =92%

(b) P(X>264)= P(Z>(264-208)/37.1)
        = P(Z>1.50) =0.0668 (from standard normal table)
            =6%
So n=242*0.0668 =16.1656

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