This why you should use confidence intervals for estimates. Use a 80% confidence interval, for example. 10% of the time, you should come in under the best case estimate. 10% of the time, it should take longer than the worst case estimate.
How do you know if your estimate is good? Would you rather bet on your estimate or on hitting one of 8 numbers on a 10-number roulette wheel? If you prefer one of the bets, adjust your estimates. If you're indifferent between the bets, the estimates accurately reflect your beliefs.
How do you know if your estimate is good? Would you rather bet on your estimate or on hitting one of 8 numbers on a 10-number roulette wheel? If you prefer one of the bets, adjust your estimates. If you're indifferent between the bets, the estimates accurately reflect your beliefs.
(The roulette wheel is from the book, How to Measure Anything by Hubbard. Confidence interval estimates are from LiquidPlanner, https://web.archive.org/web/20120508001704/http://www.liquid...)