If you multiply a set of numbers (with mean mu and standard deviation s) by a, the new mean is a*mu. The new sd is a*s. New var = (new sd)^2 = a^2 * (s)^2 = a^2 * (orig var). In this case, a = .3, so a^2 = .09, and .09*50 = 4.5.
-----Original Message----- From: gds901 [<a href="mailto://email@example.com]">mailto://firstname.lastname@example.org]</a> Sent: Thu 12/9/2004 5:10 PM To: for Teachers of AP Statistics Subject: [ap-stat] YMS Test 7C
After 14 hurricane days this fall and taking on too many new duties this year, my brain finally went on vacation today. I'm looking for a little help
Cans of soft drinks cost $0.30 in a certain vending machine. What is the expected value and variance of daily revenue (Y) from the machine, if X, the number of cans sold per day has E(X) = 125 and Var(X) = 50?
I did use a probably suspect process of elimination to come up with the key's answer "B". I didn't have trouble with E(Y), but I need help with Var(Y).
Jan Smith Auburndale High School Auburndale, FL
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