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Dear list

I am running BUGS to estimate a two-parameter IRT model. The discrimination (a) parameters are defined as follows:

for(j in 1:L) {
    a[j] ~ dlnorm(0,0.001) I(0,5)
}

My understanding (I took this code from an article) is that the "I(0,5)" prevents the value of the a's from going negative. I initialized each of the a parameters with a value of 1. When I ran the script, I obtained a "cannot bracket slice for node a[3]" error message. Any ideas as to what might cause this?

Thanks

Barth