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Evaluation of the Use and Effectiveness of Wildlife Crossings (2008) / Chapter Skim
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Appendix B - Application of Safety Performance Functions in Other States or Time Periods
Pages 132-134

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From page 132...
... ( ) 2 z y A P P E N D I X B Application of Safety Performance Functions in Other States or Time Periods
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From page 133...
... The smaller the average prediction bias, the better the model is at predicting observed data. The MPB can be positive or negative, and is given by: where n = validation data sample size; and = the fitted value Yi observation.
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From page 134...
... MSPE is typically used to assess error associated with a validation or external data set. MSE is the sum of squared differences between observed and predicted collision frequencies, divided by the sample size minus the number of model parameters.
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Key Terms

  • correlation coefficient
  • estimation data
  • data sample
  • observed collisions
  • collision frequencies

  • product moment
  • moment correlation
  • predicted collision
  • observed validation
  • recalibrated spf

  • prediction bias
  • observed data
  • minus observed
  • average model
  • value suggests

  • gof criteria
  • systematic underprediction
  • spurious instead
  • recalibration procedure
  • collision frequency

  • suggests systematic
  • sample data
  • negative prediction
  • independent variable
  • untreated segments

  • error associated
  • dispersion parameter
  • complete lack
  • recalibrated using
  • mean prediction


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