So those observations are not used to estimate the coefficient of
variables that don't change within "mother_rc", but for all others,
including the coefficients and variables that do vary at the
"mother_rc" - level and that's why the number of observations doesn't
change?
On Thu, Sep 17, 2009 at 5:09 PM, Scott Merryman
<[email protected]> wrote:
> On Thu, Sep 17, 2009 at 12:28 PM, Sue <[email protected]> wrote:
>> The only difference between the two is that the second is a regression
>> with additional fixed effects using the variable "mother_rc". I'm
>> wondering why the number of observations is the same in both
>> regressions, even though there are values of mother_rc(the group id)
>> that have only one observation and should therefore be dropped and not
>> used in the regression.
>
> Singletons will change the estimated value of the constant.
>
> Scott
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