A paired ttest is equivalent to a repeated measures ANOVA with two
levels to the repeated factor. You can see the regression equivalent
below.
webuse fuel, clear
list, clean
ttest mpg1 == mpg2
local t = r(t)
generate subject = _n
list, clean
reshape long mpg, i(subject) j(repeat)
list, clean
anova mpg repeat subject
anova, regress
test repeat
local F = r(F)
display `F' "=" `t'^2
xi: regress mpg i.repeat i.subject
On Dec 8, 2008, at 7:05 PM, josemaria wrote:
Dear Statalisters:
I am not sure whether it makes sense or not, but is there a sort of -
regress- command that allows to conduct a pair-matched -ttest-, but
with other independent variables?
I tried using -xtmixed-, but the result is not the same.
A contrived data set could be:
matching_identification outcome ocasion variable_not_matched
1 1 1 0
1 2 2 0
2 3 1 0
2 5 2 1
3 2 1 0
3 4 2 1
4 6 1 1
4 5 2 1
To perform the pair-matched ttest it is necessary to -reshape- and
to use -ttest outcome1==outcome2-, losing the independent
variable_not_matched.
Thank for any orientation.
Regards,
José Maria
Jose Maria Pacheco de Souza, Professor Titular (aposentado)
Departamento de Epidemiologia/Faculdade de Saude Publica, USP
Av. Dr. Arnaldo, 715
01246-904 - S. Paulo/SP - Brasil
fones (11)3061-7747; (11)3768-8612
fax (11)3714-2403
www.fsp.usp.br/~jmpsouza
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