yospaghetti

If you spend some time thinking out the OLS line is derived even for multiple regression models you'd realize why adding a new variable can't really worsen the model.

a) Take 1 independent and 1 dependent variable, the worst you can do is explain 0 variation!
b) Add 1 more independent variable to the model, now could you actually go below? you can't have negative r^2. so the only way to go is up. It's possible you stay at 0, but if we say you stay at 0, you it implies that this new variable is not correlated anyhow with the dependent variable.


hence by adding more and more you could only go up.



Edited 1 time(s). Last edit at Sunday, May 1, 2011 at 06:14PM by pepp.