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Re: st: dummy trapped but not sure why


From   "Austin Nichols" <austinnichols@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: dummy trapped but not sure why
Date   Wed, 23 May 2007 17:32:00 -0400

Brady--
The source of the collinearity will be more clear if you generate your
variable  intest2 in one line using the dummies, I think:

g intest2 = 100*STOH+100*STVA+100*STWV
+50*STAL+50*STKY+50*STMD+50*STNY+50*STPA+50*STSC
+33*STGA+33*STNC+33*STTN+25*STMS

On 5/23/07, bdeaton@uoguelph.ca <bdeaton@uoguelph.ca> wrote:
gen STAL = (state == "AL")
gen STGA = (state == "GA")
gen STKY = (state == "KY")
gen STMD = (state == "MD")
gen STMS = (state == "MISS")
gen STNC = (state == "NC")
gen STOH = (state == "OH")
gen STPA = (state == "PA")
gen STTN = (state == "TN")
gen STVA = (state == "VA")
gen STWV = (state == "WV")
gen STNY = (state == "NY")
gen STSC = (state == "SC")

gen intest2 = 100 if state == "OH" | state == "VA" | state == "WV"
replace intest2 = 50 if state == "AL"| state == "KY" | state == "MD" |
state == "NY"|  state == "PA" | state == "SC"
replace intest2 = 33 if state == "GA" | state == "NC" | state == "TN"
replace intest2 = 25 if state == "MISS"

regress Y intest2 STAL STGA STKY STMD STNC STOH STPA STTN STVA STNY STSC STWV

<<<this regression exhibits perfect collinearity but I'm not sure why>>>
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