Dear Statalist,
I am using xtgee (xtgee, f(nb) corr(ar1) vce(r)) to analyze an unbalanced panel data set (with 73 countries, 1980-2006). Someone suggested that I normalize my variables by subtracting the mean from each of my observations.
e.g.
YEAR VARIABLE ONE
year 1980 observation 1 for variable 1 - mean of observation of variable 1
year 1981 observation 2 for variable 1 - mean of observation of variable 1
year 1982 observation 3 for variable 1 - mean of observation of variable 1
Is this necessary?
Any opinions on this subject would be great.
Allison
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