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st: Why stata 7 and stata 8 give out different answers


From   "Maoyong Fan" <fan@berkeley.edu>
To   "statalist" <statalist@hsphsun2.harvard.edu>
Subject   st: Why stata 7 and stata 8 give out different answers
Date   Fri, 23 Apr 2004 14:37:05 -0700

I wrote a very simple program and run it on both Stata 7 intercool and Stata 8 SE, but they give me different answers.

The reason is that they drop different variables.

I wonder why is this.  Should they do the same job since I use the exact same program and data set?

Program:

clear

set memory 200m
***set maxvar 2048
set more off
set rmsg on

set logtype text
set linesize 200

***Course 32 matching estimator

use pdp_matching.dta, clear
keep	coalition_pool verbal_sat math_sat eop_status hs_gpa father_educ mother_educ language_code english non_english ethnic	admit_major math_physics	econ_business	chemistry	biology	engineering	c32_lecture	c32_times_taken	c32_year	c32_term	c32_num_grade	c32_math_98	c32_pdp_ids	c32_pdp_ids_not_pass	c32_slc_adjunct	c32_slc_adjunct_not_pass		pdp	slc	pdp_coalition_pool

drop  if    coalition_pool  ==  .
drop	if	verbal_sat	==	.
drop	if	math_sat	==	.
drop	if	eop_status	==	.
drop	if	hs_gpa	==	.
drop	if	father_educ	==	.
drop	if	mother_educ	==	.  
drop	if	language_code	==	.  
drop	if	english	==	.
drop	if	non_english	==	.
drop  if    ethnic  ==      .
drop  if    ethnic  ==      9
drop	if	admit_major	==	.
drop	if	math_physics	==	.
drop	if	econ_business	==	.
drop	if	chemistry	==	.
drop	if	biology	==	.
drop	if	engineering	==	.
drop	if	c32_lecture	==	.
drop	if	c32_year	==	.
drop	if	c32_term	==	. 
drop	if	c32_num_grade	==	.

drop    if      slc == 1

keep    if      ethnic == 1


keep  if c32_num_grade < 5 | c32_num_grade==6 | c32_num_grade==7
replace c32_num_grade=0 if c32_num_grade<=1.3 | c32_num_grade==7
replace c32_num_grade=1 if c32_num_grade>=1.7 | c32_num_grade==6

generate same_class = c32_year*100 + c32_term*10 + c32_lecture

local varlist_1 = "math_sat	eop_status	hs_gpa	father_educ	mother_educ	english		non_english	math_physics	econ_business	chemistry	biology	engineering"
local varlist_2 = "verbal_sat"

foreach var of local varlist_1 {
egen `var'_max = max(`var')
egen `var'_min = min(`var')
if `var'_max ~= `var'_min  {

local varlist_2 = "`varlist_2' `var'"
di "keep `var'"
}
else {
display "drop `var'"

}
}
display "Finish dropping"


egen pdp_sum = sum(pdp)

describe

}

log close


Please find the data on:

http://are.berkeley.edu/~fan/imbens/



Maoyong Fan

University of California


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