Hi Stefano,
How about running the regressions in logarithmic scale i.e. write something
like the following:
log.sd[i] <- Coef1*X1[i]+Coef2*X2[i]+Intercept.sd
data[i]~dnorm(mu[i],exp(log.sd[i]))
This way you can avoid inverting numbers, and your final results will have
the advantage of being a little bit easier to communicate i.e. instead of
saying that the binary predictor is associated with an X number of units
increase in the standard deviation, you can say that the predictor increases
the standard deviation by an X amount of times (unitless - does not depend
on the unit you chose to express the data).
Christos
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