The Pooled Regression a Presence of omitted effects yit=Xi B+C +et, observation for person i at time t y =x B+ci+E, T, observations in group =Xβ+c+ Ei note c=(cCp…C y =XB+C +E, 2is, T, observations in the sample a Potential bias/inconsistency of ols-depends on fixed or randomThe Pooled Regression  Presence of omitted effects  Potential bias/inconsistency of OLS – depends on ‘fixed’ or ‘random’ it it i it i i i i i i i i i i i i N i=1 i y = +c +ε , observation for person i at time t = +c + , T observations in group i = + + , note (c ,c ,...,c ) = + + , T observations in the sample  =   x β y Xβ i ε Xβ c ε c y Xβ c ε