I got a quick question about my statistical analysis for my thesis. To provide you with some background information: I am running a multifactor risk model to asses returns for certain stocks and including market returns, technology firms returns, and commodity prices (oil, natural gas and coal) as regressors.
However, I run into some trouble and let me explain why. The commodities natural gas and coal have been found to have no (significant) correlation with any of the other variables (nor dependent or independent). But running the multiple linear regression with these two variables (natural gas and coal) raises the R2 very slightly (from 0.527 to 0.528), while the coefficients are insignificant.
Can anyone maybe help explain to me how R2 can rise even though both extra included variables are insignificant and do not have correlation?
I am analysing with SPSS and Excel by the way.