Re: ISI questions on correlation

Posted by neha on Apr 17, 2012; 12:55pm
URL: http://discussion-forum.276.s1.nabble.com/ISI-questions-on-correlation-tp7472992p7473423.html

okay,,,, for question 2: i think explaining it via scatter diagram would help,, so if all the points lie on a linear equation , we say that the variables are perfectly related,, since thats the case here ,, x and y will be perfectly related,,, will have same signs in absolute terms but opposite in signs..

for question1, actually i had some difficulty in typing,, but let me try,,

Var ( n variables) = sum (i over the range 1 to n)(sum(j over the range 1 to n) of co variance of (xi,xj) ,,,,,,,,, there will be n^2 terms.
Now when u use this formula there will be n times when sigma^2 will be used for example for cov(x1,x1) and cov(x2,x2) and in rest of the cases which are n^2 -n row will be used, for instance cov (x1, x2) ,, cov(x5,x8),,, so this is how u get it,,,

hope it helps