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Towards statistically solid thinking about validation Rick.Donnelly@wsp.com | WSP | 6 May 2020 Traditional practice 2 Top five criteria (n=9) 3 Three revelations Rethinking validation: 1. Differentiate by count type 2. Trimming outliers


  1. Towards statistically solid thinking about validation Rick.Donnelly@wsp.com | WSP | 6 May 2020

  2. Traditional practice 2

  3. Top five criteria (n=9) 3

  4. Three revelations Rethinking validation: 1. Differentiate by count type 2. Trimming outliers 3. Using meta-networks 4

  5. Not all counts are created equal 5

  6. Recent outcome 6

  7. Potential error in counts Implications for counts: Assumptions: • Data are normally distribution • Distribution has mean μ and standard deviation σ • Observations are independent of one another 7

  8. Alternative view 8

  9. Some traditional stats Root mean squared error: Percent root mean squared error: 9

  10. Outlier effects on RMSE and percent RMSE 10

  11. Optimal counts? 11

  12. Meta-networks 1. Include only freeways, expressways, major arterials 2. Collapse freeway interchanges to single point 3. Meta-nodes: where these arcs intersect 4. Meta-links: single bidirectional arc between meta-nodes 5. One count per meta-link → independent observations by definition 6. Validate and visualize at the meta-network level 12

  13. Forecasting errors 13

  14. In perspective... 14

  15. Telecommuting trends over time 15

  16. Questions? 16

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