Hi,
I have a dichotomous variable (Q1) whose answers are Yes or
No.
Also I have 2 categorical explanatory variables (V1 and V2)
with two levels each.
I used logistic regression to determine whether there is an
effect of V1, V2 or an interaction between them.
I used the R and SAS, just for the conference. It happens
that there is disagreement about the effect of the
explanatory variables between the two softwares.
R:
q1 = glm(Q1~grau*genero, family=binomial, data=dados)
anova(q1, test="Chisq")
Df Deviance Resid. Df Resid. Dev P(>|Chi|)
NULL 202 277.82
grau 1 4.3537 201 273.46 0.03693 *
genero 1 1.4775 200 271.99 0.22417
grau:genero 1 0.0001 199 271.99 0.99031
SAS:
proc logistic data=psico;
class genero (param=ref ref='0') grau (param=ref ref='0');
model Q1 = grau genero grau*genero / expb;
run;
Type 3 Analysis of
Effects
Wald
Effect DF Chi-Square
Pr > ChiSq
grau 1 1.6835
0.1945
genero 1 0.7789
0.3775
genero*grau 1 0.0002
0.9902
The parameters estimates are the same for both.
Coefficients:
Estimate Std. Error z value Pr(>|z|)
(Intercept) 0.191055 0.310016 0.616 0.538
grau 0.562717 0.433615 1.298 0.194
genero -0.355358 0.402650 -0.883 0.377
grau:genero 0.007052 0.580837 0.012 0.990
What am I doing wrong?
Thanks,
--------------------------------------
Silvano Cesar da Costa
Departamento de EstatÃstica
Universidade Estadual de Londrina
Fone: 3371-4346
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