Multilevel modelling and time series analysis in ... - ERSO - Swov

Chapter 2Results and InterpretationBecause “telaps” is coded to be zero at the time of acquirement of the drivinglicence, the mean intercept β 0j indicates the average skill score at that moment.The coefficient for “telaps” indicates that on average the skill score increases byhalf a point each year that a driver has his/her licence. Note that the withinsubject variance σ 2 e is reduced as compared to the null model, suggesting thatthe measurements for each participant changed over time. However, thebetween subject variance σ 2 u0 as well, suggesting that participants varied in theeffect that telaps had for tham. Finally, the decrease of the deviance(loglikelihood) confirms that the model with “telaps” fits better than the onewithout.2.4.1.3. Two-level random intercept model with two predictorsThe question “treated” in this simulated study is whether it is the number ofyears passing or rather the increase of experience that make older drivers lessaccident prone than younger ones. To investigate this, the driving experience(measured in 1000 km driven) is taken up into the model in parallel with the timeelapsed (telaps).Model formulation• Click “Add Term” at the bottom of the Equations window• Select “experience” from the “Variable” drop-down window• Click “Done”• To estimate this model press “Start”