# Re: st: Chi-square test for Categorical Data Analysis

 From Maarten buis <[email protected]> To [email protected] Subject Re: st: Chi-square test for Categorical Data Analysis Date Thu, 20 Sep 2007 22:09:04 +0100 (BST)

```--- Maarten buis <[email protected]> wrote:
> In the example below I simulate the the results if we had the
> continuous data, use -intreg- with log transformed endpoints, and log
> transformed mid-point scaling. All three methods seem to perform ok.

In the example below you see an altarnative simulation in which both
-intreg- and mid-point scaling don't do so well:

*---------------- begin example -------------------
set more off
set seed 12345

sysuse nlsw88, clear
gen lnwage = ln(wage)

capture program drop sim
program sim, rclass
sysuse nlsw88, clear
gen ran = uniform()
sort ran
keep in 1/1000
egen wagecat = cut(wage), ///
at(0, 5, 10, 20, 30, 50)

gen wagecat2 = wagecat
recode wagecat2 ( 0 =  5) ///
( 5 = 10) ///
(10 = 20) ///
(20 = 30) ///
(30 = 50)
gen lncat  = ln(wagecat + .5)
gen lncat2 = ln(wagecat2)

gen mid = wagecat
recode mid ( 0 =  3  ) ///
( 5 =  7.5) ///
(10 = 15)   ///
(20 = 25)   ///
(30 = 40)
gen lnmid = ln(mid)

gen lnwage = ln(wage)
end
simulate xcat=r(xcat) xmid=r(xmid) xcont=r(xcont) ///
, reps(1000): sim
twoway kdensity xcont ||            ///
kdensity xcat  ||            ///
kdensity xmid,               ///
xline(`pop')                   ///
ytitle("density")            ///
legend(order(1 "continuous"  ///
"wage"        ///
2 "intreg"      ///
3 "mid point"   ///
"scoring"))
sum
*--------------- end example ------------------
(For more on how to use examples I sent to the Statalist, see
http://home.fsw.vu.nl/m.buis/stata/exampleFAQ.html )

Hope this helps,
Maarten

-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------

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