Last Friday, we asked you to estimate a confidence interval for ten questions as a test of your decision making ability. Let's see how you did.

If you were honest and thoughtful about your answers, at a 90% confidence interval your estimated intervals should contain the correct answer nine times out of ten. In other words, only a single answer would be outside the high and low estimates you wrote down last Friday.

1. Length of the Nile River (in miles): 4187
2. Diameter of the moon (in miles): 2160
3. Weight of an empty Airbus 380 (in pounds): 606,000
4. Year in which Wolfgang Amadeus Mozart was born: 1756
5. Gestation period of an Asian elephant (in days): 645
6. Air distance from Chicago to Shanghai (in miles): 7,061
7. Year the first spacecraft landed on the moon: 1959
8. Area of US national parks (in square miles): 131,875
9. Year in which Attila the Hun died: 453 AD
10. Average population density of the US (in people/sq mi): 83.6

How did you do? Since your confidence intervals were entirely under your control, getting less than nine answers within your range indicates overconfidence in your abilities. A little humility is a good thing.

P.S. Many factors contribute to bad decisions, including making false assumptions. Most people guess 1969 for question #7 because they equate "moon landing" with "the first manned moon landing" in 1969, but that was not what the question asked. The Soviets (crash) landed Luna 2 on the moon on September 12, 1959.

© 2010 Institute of Management Consultants USA