The models were based on crash data gathered over a 5-year period, using a broad number of explanatory variables related to exposure, geometry, design consistency and roadside features.
Thus we made the decision to omit these variables in favour of utilising a broader number of survey years, increasing the number of participants included in the heaviest day analyses by extending the sample to include all survey years for which the heaviest day variable was available (1999-2008) and permitting the analysis of average weekly alcohol consumption over the previous year (1998-2002).
In addition to the dummy variable that indicates whether an education programme is narrow or broad, a number of control variables are used in the estimated regression analyses.
Comparing the predictive performance of the models outside the Slider turtle's native range, selection of a lower number of variables was associated with a broader area classified as suitable in a limited number of models (<10%).
Under a broad set of assumptions, if datasets of various sample sizes and number of variables can be produced, an inference method then can be tested extensively, especially against its sensitivity to dimensionality.
This high number of variables gives a unique chance to catch a broad range of biological processes but, at the same time, poses significant challenges to statistical methods of analysis.
Because the goals of the study were broad-based and descriptive, a decision was made to cover a large number of variables using single items and small modules, rather than including a restricted set of detailed "gold standard" measures.
This difficulty stems from the number of variables that ideally should be accounted for within a sample of persons with ASDs, including the broad range of symptoms, the chronicity of illness, differences in IQ, and psychiatric comorbidity.
