# testing significance of brand 14[21]
p_load(aod)
s <- vcov(model_1)
head(s)
wald.test(b = coef(model_1), Sigma = s,Terms = 21)
## value obtained: phi 0.33. This level will be grouped with the standard insurance[1].

# Grouping Brand 1 (standar insurance) and 14
baseFREQ$brandy = baseFREQ$brandx
baseFREQ$brandy[baseFREQ$brandx %in% c("1","14")] = "1"

model_2 <-glm.nb(nclaims ~ zone_ + vehcut + agecut + as.factor(brandy) +
                 fuel + offset(log(exposition)), data = baseFREQ)
summary(model_2)