Hi.

I am doing two time-series regressions, both regressions contain 3 mutual variables with several other variables in them.

Set 1: A B C D E F G

Set 2: A B C H I J K L M

I am running covariance matrix (looking at the correlation amongst variables for both regressions). However, since the 3 mutual variables are present for both regressions, do I still include these 3 variables in the covariance matrices for both regression? I am not sure because the correlation coefficients for the same mutual variables are different.

For instance,

Set 1: A-B = 0.5678

Set 2: A-B = -0.4892

Any helps will be greatly appreciated.

Thank you!

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