QZ 2-B - However, each time the server crashes, Initech...

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STAT 400 Fall 2011 Version B Name ANSWERS . Quiz 2 (10 points) Be sure to show all your work; your partial credit might depend on it. No credit will be given without supporting work. 1. (10) Initech does part of its business via Internet. However, because of the high traffic, the server that carries the company’s website often crashes. The probability distribution of the number of server crashes per month, X, is given below: x f ( x ) x f ( x ) x 2 f ( x ) 0 1 2 3 0.15 0.35 0.45 0.05 0 0.35 0.90 0.15 0 0.35 1.80 0.45 1.40 2.60 If the server does not crash, Initech ’s monthly profit from the website is $80,000.
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Unformatted text preview: However, each time the server crashes, Initech looses $30,000. Therefore, Initech s monthly profit from the website (in thousands of $) is Y = 80 30 X. Find Initech s average monthly profit from the website and its standard deviation. E ( X ) = x x f x all ) ( = 1.40 . [ ] [ ] 2 all 2 2 2 X E ) ( X E X E X Var ) ( ) ( ) ( ) (-=-= x x f x = 2.60 -( 1.40 ) 2 = 0.64 . SD ( X ) = 64 . = 0.80 . E ( Y ) = 80 30 E ( X ) = 80 30 1.40 = 38 . $38,000 . SD ( Y ) = | 30 | SD ( X ) = 30 0.80 = 24 . $24,000 ....
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