7.1 Count First

What do you think the right answer is? Is it the answer of 335, created by Bill, whose specialty is estimating crowd sizes? Is it the answer of 385, derived by Karl from a few reasonable assumptions? Is it Lucy's 365, also derived from a few reasonable assumptions? Or is the right number the 407 that was counted by the ticket scanner? Is there any doubt in your mind that 407 is the most accurate answer? For the record, the story ended by your table proposing the answer of 407, which turned out to be the correct number, and your table was served dessert first.

One of the secrets of this book is that you should avoid doing what we traditionally think of as estimating! If you can count the answer directly, you should do that first. That approach produced the most accurate answer in the story.

If you can't count the answer directly, you should count something else and then compute the answer by using some sort of calibration data. In the story, Karl had the historical data of knowing that the banquet was planned to have 5 people per table. He counted the number of tables and then computed the answer from that.

Similarly, Lucy based her estimate on the documented fact of the room's occupancy limit. She used her judgment to estimate the room was 70 to 80 percent full.

The least accurate estimate came from, Bill, the person who used only judgment to create the answer.

Tip #30

Count if at all possible. Compute when you can't count. Use judgment alone only as a last resort.