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Re: st: Bias in a zero truncated poisson
From
Austin Nichols <[email protected]>
To
[email protected]
Subject
Re: st: Bias in a zero truncated poisson
Date
Mon, 1 Nov 2010 10:42:57 -0400
Laurie Molina <[email protected]>:
First, read the manual entry on -ztp- and then try:
sysuse auto, clear
ztp trunk mpg
predict t_uncon
predict t_con, cm
su trunk t_*
What is it you want these predictions for?
On Sun, Oct 31, 2010 at 12:11 PM, Laurie Molina <[email protected]> wrote:
> Hi all,
> My dependent variable is a count data variable that takes only positive values.
>
> I am running:
> ***
> ztp depvar indepvars
> predict number
>
> sum depvar
> sum number
> ****
> but the mean of depvar is not the same as the mean of number.
>
> On the other hand if i run
> ******
> poisson depvar indepvars
> predict number2
>
> sum depvar
> sum number2
> ******
>
> the mean of depvar is the same as the mean of number2.
>
> Why is this happening?
> Aren't ztp estimates unbiased estimates?
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