Unformatted text preview: mean μ Y = 176 mg/dLi and standard deviation σ Y = 30 mg/dLi. High cholesterol is any level greater than 200 mg/dLi. (a) (3 points) What is the probability that a randomly selected 17year old will have high cholesterol, P ( Y > 200) ? Answer: normalcdf(200,10 ∧ 99,176,30) gives 0.212. Otherwise you can use a table and compute P ( Y > 200) = 1P ( Y < 200) = 1P ± Y176 30 < 200176 30 ¶ = 1P ( Z < . 8) = 1. 7881 = 0 . 212 (b) (2 points) What is the 78.8th percentile of cholesterol levels, i.e. the number k such that P ( Y < k ) = 0 . 788 ? (Hint: what is P ( Y < 200) from part (a)?) Answer: You could use invNorm(0.788,176,30) to get 200 or else use part (a) directly noting that P ( Y < 200) = 1. 212 = 0 . 788 ....
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 Fall '09
 Hendrix
 Normal Distribution, Probability, Standard Deviation, serum cholesterol level

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