• Box–Cox transformation;
  • Centile interval;
  • Cubic splines;
  • Non-normal distributions;
  • Nonparametric smoothing;
  • Skewness;
  • Variance heterogeneity

This paper analyses rent data obtained from a survey conducted for the 1994 rental guide for the city of Munich. We describe how mean and dispersion additive models can be applied to the situation where both the mean and the heterogeneity in the dependent variable, rent here, need to be modelled by using parametric and/or nonparametric functions of explanatory variables. The skewness in the rent variable is dealt with either by using a Box–Cox transformation to normality or by modelling the rent variable by using a family of skew distributions. A gamma distribution model was chosen to provide centiles estimates and intervals for the rent variable.