| (One intermediate revision by the same user not shown) | |||
| Line 1: | Line 1: | ||
| − | Does any one know what to do to the variance when multiplied by a number? I know that when added together: | + | a)Does any one know what to do to the variance when multiplied by a number? I know that when added together: |
<math> Z = X + Y => Var(Z) = Var(X + Y) </math> | <math> Z = X + Y => Var(Z) = Var(X + Y) </math> | ||
| Line 7: | Line 7: | ||
<math> Z = aX => Var(Z) = a^2Var(X) </math> | <math> Z = aX => Var(Z) = a^2Var(X) </math> | ||
| − | This may be completely wrong... | + | This may be completely wrong... Any ideas? |
b)Since the equation for the correlation coefficient is | b)Since the equation for the correlation coefficient is | ||
<math> p(x,y) = \frac{cov(X,Y)}{\sqrt{var(X)}\sqrt{var(Y)}} </math> | <math> p(x,y) = \frac{cov(X,Y)}{\sqrt{var(X)}\sqrt{var(Y)}} </math> | ||
Latest revision as of 11:10, 8 December 2008
a)Does any one know what to do to the variance when multiplied by a number? I know that when added together:
$ Z = X + Y => Var(Z) = Var(X + Y) $
I seem to remember something like:
$ Z = aX => Var(Z) = a^2Var(X) $
This may be completely wrong... Any ideas?
b)Since the equation for the correlation coefficient is
$ p(x,y) = \frac{cov(X,Y)}{\sqrt{var(X)}\sqrt{var(Y)}} $
