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 3. Using meta-networks 4
Not all counts are created equal 5
Recent outcome 6
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
Alternative view 8
Some traditional stats Root mean squared error: Percent root mean squared error: 9
Outlier effects on RMSE and percent RMSE 10
Optimal counts? 11
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
Forecasting errors 13
In perspective... 14
Telecommuting trends over time 15
Questions? 16
Recommend
More recommend