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st: RE: sample size reduced significantly


From   Arya Eskamani <Arya.Eskamani@assist-rx.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   st: RE: sample size reduced significantly
Date   Thu, 11 Apr 2013 20:34:35 +0000

In your explanatory variables, do you have any rows that with a missing field?  When you run an OLS it only runs on observations for which all data is available.  

Try seeing if you do by using -codebook [varname]- , it will tell you if it holds any missing values. Hope this helps :)

Arya Eskamani, M.S.
Project Manager
4700 Millenia Blvd | Ste 500 | Orlando, FL 32839
407.367.2880 Phone | 877.313.4412 eFax 
www.assist-rx.com | arya.eskamani@assist-rx.com


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Yu Chen, PhD
Sent: Thursday, April 11, 2013 4:17 PM
To: statalist@hsphsun2.harvard.edu
Subject: st: sample size reduced significantly

Dear Statalist,
I have several variables with each of them having at least 6000 observations (non-missing values). However, when I put them into OLS regression, the number of observations reduced to only about 1000. I cannot figure out what causes the problem. Could you please help me find out the causes? What code can I use to analyze the problem?
Thank you in advance.

Yu Chen
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