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Unformatted text preview: HW 3 SOLUTIONS Chapters 4 and 5 (from 3 rd ed. of text) 1. 5.23. A certain assay for serum alanine aminotransferase (ALT) is rather imprecise. The results of repeated assays of a single specimen follow a normal distribution with mean equal to the ALT concentration for that specimen and standard deviation equal to 4 U/Li (as in Exercise 4.40). Suppose a hospital lab measures many specimens every day, and specimens with reported ALT values of 40 or more are flagged as “unusually high.” If a patient's true ALT concentration is 35 U/Li find the probability that his specimen will be flagged as “unusually high” a. if the reported value is the result of a single assay Correct: The result of a single assay is like a random observation Y from the population of assays. A value Y ≥ 40 will be flagged as “unusually high”. TI84 normalcdf(40, E99, 35, 4) = 0.1056 Thus, Pr{specim en will be flagged as “unusually high”} = 0.1056. b. Find the 99th percentile of this distribution. TI84 invNorm(.99, 35, 4) = 44.31 U/Li c. if the reported value is the mean of three independent assays of the same specimen The reported value is the mean of three independent assays, which is like the mean Y of a sample of size n = 3 from the population of assays. A value ¡ ≥ 40 will be flagged as “unusually high.” We are concerned with thehigh....
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 Fall '09
 Hendrix
 Normal Distribution

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