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st: RE: RE: FW: zinb help


From   "Rajesh Tharyan" <R.Tharyan@exeter.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: RE: FW: zinb help
Date   Tue, 21 Mar 2006 22:38:46 -0000

Hi,

I am seriously sorry nick I wasn’t trying to be clever ... but I did go
through help and the manuals .. I was looking at the descriptions which does
not say that clearly..it says..

zinb estimates a maximum-likelihood zero-inflated negative binomial
regression of depvar on varlist,where depvar is a nonnegative count
variable.

Of course I didint understand the syntax diagram .. my fault.. but now I
understand that Typing [ and ] means the varlist is optional.

So the command will be zinb (var),inflate(var).. is that right?

Thanks 
Rajesh 


This refers to the exchange below. 

The syntax diagram for -zinb- 
makes it clear that independent variables 
need not be specified: thus -zinb- may be
used to fit a distribution to a response 
(dependent) variable alone. 

So, again, do please read the help. 

Nick
n.j.cox@durham.ac.uk 

--------------------------- 28 February 2006 
Stata offers many commands for these distributions
and others in the same territory. 

Please use -help-, -search- and the manual before
sending such queries to the list. 

> I have a dataset which looks like the one below
> 
>            Individual 1      		individual 2
> Time  	count             	 count
> 1		0                   	  1
> 2		1				  0
> 3		0				  0	
> 4		0				  0
> 5		3				  1
> 6		0                         0
> 7		1                         0
> 
> Time represents months and count represents the occurance of 
> an event. I
> understand that count might follow a  zero inflated poisson 
> distribution or
> a negative binomial  distribution. 
> 
> Are there any stata command to check if the data fits these 
> distributions?
> (just like we have the shapiro-wilk test for normality.).
> 
> My objective is to see if there is any increase in the counts 
> between say
> period1 (time 1 to 3) and period2 (time 4 to7) for each 
> individual. And for
> all individuals taken together...

----------------------------------------------------------------------------
----

Rajesh Tharyan
 
> I have asked this question before but got told off... but I 
> am no closer to
> finding an answer... I know there is "nbfit"  to fit a  
> negative binomial
> distribution to a single variable by the method of maximum 
> likelihood. Is
> there something similar to fit a zero inflated negative binomial
> distribution to a single variable? I found nbvargr which fits 
> a poisson and
> a negbinomial dist to a variable but nothing on zero inflated 
> distributions.
> 
> The only commands related to zero inflated models I found were zip and
> zinb...
> 
> I am sorry if it is still a very dumb question.. 

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