Correlation Question

[HasselbeckFan]

Hello all! I have an exam coming up in statistics and one thing that is really confusing me is the equation for correlation.. or solving for "r" basically.

Here is one example I am stuck on:

Given the following:
mean of x - 51
std dev of x - 8.48
mean of y - 91.5
std dev of y - 3.27
n = 6
r = ?

I think the thing that is really tripping me up.. is the equation.. can someone be kind enough to explain how to solve for "r" using the correlation equation:

r = 1    ∑ (Xi-mean of x) (Yi - mean of y) 
  n-1          Sx               Sy

Thanks!

 

[JakeD]

Hello all! I have an exam coming up in statistics and one thing that is really confusing me is the equation for correlation.. or solving for "r" basically.

Here is one example I am stuck on:

Given the following:
mean of x - 51
std dev of x - 8.48
mean of y - 91.5
std dev of y - 3.27
n = 6
r = ?

I think the thing that is really tripping me up.. is the equation.. can someone be kind enough to explain how to solve for "r" using the correlation equation:

r = 1    ∑ (Xi-mean of x) (Yi - mean of y) 
  n-1          Sx               Sy

Thanks!

You cannot solve for \(\displaystyle r\) using the information given. \(\displaystyle \sum_i (X_i - \bar{x})(Y_i - \bar{y})\) is a sum over 6 observations. \(\displaystyle X_i\) represents the \(\displaystyle i^{th}\) observation of the variable \(\displaystyle X.\) So you need the \(\displaystyle (X,Y)\) pairs for all the 6 observations.