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

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Chapter 2Results <strong>and</strong> InterpretationThe <strong>in</strong>tercept β 0j now presents the average speed at LengthCentred = 0 (i.e. fora car of average length) <strong>and</strong> the coefficient <strong>in</strong> front of LengthCentred <strong>in</strong>dicatesits slope: the change <strong>in</strong> speed per unit of length (here meters). The deviance (-2*loglikelihood) decreased by 70, i.e. the <strong>in</strong>troduction of car length as apredictor significantly improved the model.2.2.1.4. Two-level r<strong>and</strong>om <strong>in</strong>tercept, r<strong>and</strong>om slope modelTo <strong>in</strong>vestigate whether the relation between speed <strong>and</strong> the length of a car wasthe same at all measurement locations, the slope of Length will now be allowedto vary r<strong>and</strong>omly across locations too.Model formulation• Click on the Length• Check the box j (IDlocation)• Estimate the parameters by click<strong>in</strong>g on “Start”Results <strong>and</strong> Interpretation

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