Hi:
I am not sure you using the correct terminology to describe you model.
You say "mediated"--which means "carries the effect". If you want to
check whether x3 mediates the effect of z on y you need to estimate
ivprobit y = x1 x2 (z =x3),
overid
(download the -overid- ado)
Then if you want to know whether the indirect effect is significant:
nlcom [z]x3*[y]z
Now if you are talking about moderation, this is another story--this
means "changes the nature of the relation between z and y". Here you
estimate:
logit y z x1 x2 x3 x3*z
Moderation occurs if the beta of the x3-z interaction is significant.
HTH,
J.
____________________________________________________
Prof. John Antonakis
Associate Dean Faculty of Business and Economics
University of Lausanne
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____________________________________________________
On 12.06.2009 14:43, [email protected] wrote:
I am trying to determine the statistical significance of the change in
a parameter estimate for a predictor variable in a logistic regression
when another predictor is added In other words, I have two models;
model 1: logit y on z x1 x2
model 2: logit y on z x1 x2 x3.
I want to check if the association between y and z is mediated in part
by x3. I have already determined that z is associated with x3 and that
y is associated with x3.
I have tried to do this with the suest command but I do not trust the
results since the two regressions are not run on independent samples.
I would be grateful for any guidance from anyone on how to perform a
valid statistical test the change in the parameter estimate for z when
x3 is added to the regression.
John T. Schousboe
University of Minnesota
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