Thread: Word problem dont know where to begin
View Single Post
  #2  
Old January 2nd, 2009, 04:08 PM
nzmathman nzmathman is offline
Member
  
Join Date: Dec 2008
Location: Auckland, New Zealand
Posts: 182
Country:
Thanks: 10
Thanked 89 Times in 85 Posts
nzmathman will become famous soon enough
Default
a) The mean,
E(C) = \sum_1^i \;C_i \times P(C = C_i)
= 0 \times 0.4 + 1 \times 0.3 .....


Var(C) = E(C^2) - [E(C)]^2

where E(C^2) = \sum_1^i \;(C_i)^2 \times P(C = C_i)
= 0^2 \times 0.4 + 1^2 \times 0.3 .....

and remember standard deviation, \sigma_c = \sqrt{Var(C)}


b) For any two random variables X and Y, E(X + Y) = E(X) + E(Y) and Var(X + Y) = Var(X) + Var(Y)


c) For this question, use the rules E(aX + bY) = aE(x) + bE(Y) and Var(aX + bY) = a^2Var(X) + b^2Var(Y)
The following users thank nzmathman for this useful post:
Donate to MHF