## Notation

The discussion here is in the context of the usual
panel structure,

with the specification of *u*_{it} dependent on the particular
model. The total number of observations
.
For the balanced data case, *T*_{i} = *T* for all *i*.
The *M* × *M* covariance matrix of *u*_{it} is denoted by **V**.
Let **X** and **y** be the independent and dependent variables
arranged by cross section and by time within each cross section.
Let **X**_{s} be the *X* matrix without the intercept.
Generally, all other notation is specific to each section.

Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.