Long-term experiments are commonly used tools in agronomy, soil science and other disciplines for comparing the effects of different treatment regimes over an extended length of time. Periodic measurements, typically annual, are taken on experimental units and are often analysed by using...

Maximum likelihood estimation for a joint location/dispersion model has been found occasionally to experience convergence problems when applied to experiments of the 2k factorial series. We explore these problems and identify models for which the likelihood diverges or is multimodal. We derive...