1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Mean and standard deviation for linear combinations

  1. Jan 22, 2009 #1
    1. The problem statement, all variables and given/known data

    Data set in X with mean xbar = 100 and standard deviation Sx = 10

    Find ybar and Sy for 2(Yi-5)/10 + 7



    2. Relevant equations



    3. The attempt at a solution

    All the problems I have seen are in the form yi = axi + b in which case the mean ybar = a(xbar) + b and Sy = aSx

    What does Yi represent exactly? How does it relate to xi?
     
  2. jcsd
  3. Jan 23, 2009 #2

    Mark44

    Staff: Mentor

    I don't see how you can find ybar and Sy unless you know the relationship between X and Y.

    You show an expression 2(Yi - 5)/10 + 7 = (Yi - 5)/5 + 7. Could this be Xi?

    If that's the case, then you can solve for Yi.

    Xi = (Yi - 5)/5 + 7
    ==> Xi - 7 = (Yi - 5)/5
    ==> 5(Xi - 7) = (Yi - 5)
    ==> 5(Xi - 7) + 5 = Yi
    or
    Yi = 5Xi - 30
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Mean and standard deviation for linear combinations
Loading...