Val�rie:
Easier, and thus less error prone is to use the -lincom- command, see
example below:
*------------------------begin example-----------------------------
sysuse auto, clear
recode rep78 1=2 /*category 1 is so small that I combined it with category 2*/
xi3: logit foreign e.rep78 /*combining xi3 with the e prefix is an easy way
to get the coding scheme you want*/
lincom -1*(_b[_Irep78_3] + _b[_Irep78_4] + _b[_Irep78_5])
*------------end example----------
HTH,
Maarten
-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands
visiting adress:
Buitenveldertselaan 3 (Metropolitan), room Z214
+31 20 5986715
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
----- Val�rie Jooste wrote:
> Could you please confirm if I'm right by then calculating
> SE(_b[group1]) using the property of variance :
> var(X2+X3+X4+X5)=var(X2)+var(X3)+var(X4)+2covar(X2X3)+2covar(X2X4)
> +2covar(X2X5)+2covar(X3X4)+2covar(X3X5)+2covar(X4X5)
---- Val�rie Jooste also wrote:
> OOOps I forgot +var(X5) in formula
*
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