Communicating and evaluating probabilities

1. Communicating and evaluating probabilities David Spiegelhalter MRC Biostatistics and Statslab CSI day: September 2011 With thanks to Mike Pearson and Ian Short

2. Summary • Visualisations • Met Office experiment • Scoring rules for a quiz Spiegelhalter DJ, Short I and Pearson MP (2011) Visualisation of uncertainty about the future. Science333, 1393-1400

3. Kickoff.co.uk

4. “Cone of Uncertainty” for hurricane warnings

5. 2011: NBC News for Hurricane Katia ‘Possible futures’ metaphor

6. William Hill 1st June 2011

9. Quantifying your ignorance • Think whether you prefer (A) or (B) for each question • Then think of how confident you are with your answer • Give your confidence a number 5 to 10 • Score yourself when you hear the correct answer

10. A short quiz 1. Which is higher, A) the Eiffel tower, B) Canary Wharf? A (324m vs 235m) 2. Who is older, A) Prince William or B) Kate Middleton ? B (Born 21/6/82 vs 9/1/82) • In the IMDB rankings (20/05/2011), which film comes higher, A) Toy Story 3 or B) WALL.E? A (34th vs50th) 4. Which is larger, A) Belgium or B) Switzerland? B (30 vs 41 000 sq km) 5. Which is bigger, A) Venus B) Earth? B (6051 vs 6371 km radius) 6. Who died first, A) Beethoven or B) Mozart? B (1827 vs 1791)

11. Online quiz

12. Scoring the quiz

13. Current issue: how to break down someone’s total score

14. Cochrane video