(a) Run the regression with all years
(c) Test if the coefficients on on-base percentage and slugging are equal. (d) Rerun the regression for each year separately saving the coefficients on OBP and SLG for each year.
I am little confused about the regress command, is it can only regress one variable at a time? It doesn't work when I tried to regress (all variable names isolated with space) but it doesn't work.