Dear Users,

I am fitting a spatial model a multilevel data (mouth-tooth-surface) of very small prevalence. Therefore in my case every person will act as a map. I am looking at a binary outcome of a tooth surface which is nested in the tooth and nested in the mouth. So I have a surface-tooth-mouth hierarchy. Hence I am putting random effects at tooth and mouth level + a CAR spatial effect. The neighborhood is as follows: tooth surfaces are neighbors if they belong to the same tooth. The sample of my program is shown below.

cat("model {
for (i in 1:N) {

y[i] ~ dbern(p[i])
logit(p[i])<- beta[1] + beta[2]*GENDER[i] + beta[3]*AGE1[i] + beta[4]*xcood1[i] + beta[5]*ycood1[i] +
               bm[idd2[i]] + bt[tid2[i]] + be[ex2[i]] + v[i]

}

        for(m2 in 1:n1)
          {
             bm[m2]~dnorm(0,tau.bm)
          }

        # Level 3: Tooth
        for(t2 in 1:n2)
          {
             bt[t2]~dnorm(0,tau.bt)
          }

        for(e2 in 1:n3)
          {
             be[e2]~dnorm(0,tau.be)
          }

v[1:N] ~ car.normal(adj[], weights[], num[], prec.v)


for(s in 1:5){beta[s] ~ dnorm(0.0,1.0E-6)}

       sigma.bm ~ dunif(0.0,100)
       sigma2.m<-pow(sigma.bm,2)
       tau.bm<- 1/sigma2.m

       sigma.bt ~ dunif(0.0,100)
       sigma2.t<-pow(sigma.bt,2)
       tau.bt<- 1/sigma2.t

       sigma.be ~ dunif(0.0,100)
       sigma2.e<-pow(sigma.be,2)
       tau.be<- 1/sigma2.e

       sigma ~ dunif(0.0,10)
       v.v<-pow(sigma,2)
       prec.v<- 1/v.v

}",file="model2f.txt")

I am having extremely difficult convergence problems. I would appreciate if someone can help me how i can improve convergence. I am using WinBUGS and OpenBUGS.

Kind regards,
Timothy

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