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Mathematical Methods for Physics and Engineering - Matematica.NET

Mathematical Methods for Physics and Engineering - Matematica.NET

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PROBABILITY◮Sawmill A produces boards whose lengths are Gaussian distributed with mean 209.4 cm<strong>and</strong> st<strong>and</strong>ard deviation 5.0 cm. A board is accepted if it is longer than 200 cm but isrejected otherwise. Show that 3% of boards are rejected.Sawmill B produces boards of the same st<strong>and</strong>ard deviation but of mean length 210.1 cm.Find the proportion of boards rejected if they are drawn at r<strong>and</strong>om from the outputs of A<strong>and</strong> B in the ratio 3:1.Let X = length of boards from A, sothatX ∼ N(209.4, (5.0) 2 )<strong>and</strong>( ) ( )200 − µ 200 − 209.4Pr(X

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