why does correl(x,y) NOT equal covar(x,y)/stdev(x)*stdev(y) in excel??!

leopons_rock -

Excel's Help shows the formulas for each function.

CORREL uses n, COVAR uses n, and STDEV uses n-1, where n is the sample size.

CORREL(x,y) does equal COVAR(x,y)/(STDEVP(x)*STDEVP(y)).

- Mike Middleton
http://www.DecisionToolworks.com
Decision Analysis Add-ins for Excel


"leopons_rock" wrote in message
...

why does correl(x,y) NOT equal covar(x,y)/stdev(x)*stdev(y) in excel??!

Hi. A math program showed Covar using a poplulation size.( ie n-1, not n)
In other words, if the size is 4, then it divided by 3.
So, with n=4 data points, try muliplying by n/(n-1)
Make sure you use ( ) around the denominator also.
(Not always perfect, but I trust math programs much more than Excel.)

=CORREL(y,x)=COVAR(x,y)/(STDEV(x)*STDEV(y))*4/3

- TRUE

HTH
Dana DeLouis


"leopons_rock" wrote in message
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why does correl(x,y) NOT equal covar(x,y)/stdev(x)*stdev(y) in excel??!

STDEVP(x)*STDEVP(y)

Well, duh! Thanks !! :~

Dana


"Mike Middleton" wrote in message
...
leopons_rock -

Excel's Help shows the formulas for each function.

CORREL uses n, COVAR uses n, and STDEV uses n-1, where n is the sample
size.

CORREL(x,y) does equal COVAR(x,y)/(STDEVP(x)*STDEVP(y)).

- Mike Middleton
http://www.DecisionToolworks.com
Decision Analysis Add-ins for Excel


"leopons_rock" wrote in message
...

why does correl(x,y) NOT equal covar(x,y)/stdev(x)*stdev(y) in excel??!