==Fitting the regression line== 

 In  ==Fitting the regression line== shouldn't the expression immediately before the one containing Cov & Var have 1/n as the multiplier before the - x.y and before the - x^2 terms?  This is the form of the expression which is often used in computing to generate a straight-line fit to set of "bumpy" data. As expressed here it does not work and moreover does not follow mathematically from the preceding expression! However with the 1/n terms in place it appears to produce the correct result. 1/n is unique to these two terms ONLY and therefore does NOT cancel?!? But then I am a Physicist and not a Mathematician so I may have missed something??? Chris B. 6:45pm PST on 24th. Mar. 2013.  — Preceding unsigned comment added by     

 :Have a look at the section below "By using calculus" which steps through a derivation and also mentions multiplying top and bottom by N. Incidentally, I also studied Physics.    

 ==beta hat== 

 I was confused by the formula for , I wonder if the second one should have more parentheses around sums, like 

 (as product has precedence over summation) - but I am no mathematician nor English, so perhaps do not know conventions. Can someone look at it and possibly fix it? I know it is logical to at least assume the parentheses, but this is introductory and should be as precise as possible.