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Re: st: xtpoisson, fe: 42 groups (93 obs) dropped because of all zero outcomes! Why?


From   nicola.baldini2@unibo.it
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: xtpoisson, fe: 42 groups (93 obs) dropped because of all zero outcomes! Why?
Date   Mon, 05 May 2008 18:24:11 +0200

A group in this case is all the observations which share the same value of the group/panel variable "i", as setted by the -tsset- command. If all the observation with the same value of such variable have a zero outcome, then the group is deleted. I am worried about the ratio between obs and groups: about 2 is quite a small number
Nicola

At 02.33 01/05/2008 -0400, "ippab ippab" wrote:
>Hi Everyone,
>
>I am running a fixed effects model with "xtpoisson, fe" command.  I am
>trying to understand why the software is dropping a few observations
>because of the following reason: "42 groups (93 obs) dropped because
>of all zero outcomes".   More specifically, I am confused with the
>term all zero outcomes.  How is it determining this 42 groups?  My y
>variable is a count and includes zeros for more than 42 groups.
>Clearly, it is dropping a subset of the groups with zero y variable.
>May be the answer is quite trivial; unfortunately, I am not getting
>it.  I would really appreciate any help.
>
>Thanks a lot.
>
>ippab 

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