In article <[EMAIL PROTECTED]>, janne <[EMAIL PROTECTED]> wrote:
>I have a correlation formula I don't get to work. And we must use this >formula on the test. Let me give you an example: Let's say X and Y >are: [example omitted] >As you see the answer is zero. What do I do wrong? Nothing. For any given set of data the sum of the difference between the data points and their mean will always be zero. The formula at the URL you posted isn't asking you to sum the differences from the mean. The summation notation Sigma(x-xbar)(y-ybar) means to take each x,y pair, subtract the mean, multiply then sum. This will not sum to zero. Likewise, the notation Sigma(x-xbar)^2 means to subtract the x-mean from each x data sample, square the result then sum all of the values. This too will not be zero unless all of the x data points are identical. -- - PGPKey fingerprint: 6DA1 E71F EDFC 7601 0201 9243 E02A C9FD EF09 EAE5 ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =================================================================