Hi Everyone,

I estimate a linear model with OLS. I have two independent variables, x1 and x2. When I run regress y x1, I find that x1 is significant. When I run regress y x1 x2, x1 loses statistical significance as I expect since I argue that x2 matters for the changes in y not x1. Althoug the correlation between x1 and x2 is -0.25, (so there is no multicollinearity problem), I was suggested to orthogonalize two variables to make sure that actually x2 significantly explains y, not x1. When I orthognalize x2 and x1 (orthog x2 x1, gen (newx2 newx1)), t values remain almost same. When I orthognalize x1 and x2 (orthog x1 x2, gen (newx1_alt newx2_alt)), the coefficient on x1 becomes significant again. Can anyone help me how interpret these results? Should I use orthog here and if so, which order I should rely on? I read the help file but couldn't understand which one fits into my case better.

Thanks in advance.

Best,
Ulas