Yes, I also get -1 using the definitions given in the Mathematica documentation. I agree that 7 is probably an error. My Mathematica is seven years old, and I just wanted to make sure somebody had not decided to change a definition. Thanks for your interest and help.
Yes, that is what I see in version 7. But check here: http://www.wolfram.com/language/fast-introduction-for-math-students/statistics/
In[1]:= Correlation[{1, 3, 5}, {6, 4, 2}] Out[1]= -1 In[2]:= $Version Out[2]= "11.0.1 for Microsoft Windows (64-bit) (September 20, 2016)"
