Accuracy V.S.Precision

Went to Dana's Software Engineering invited speaker again...
Again from Agile Group, talking about project Estimation.

Getting to the margins of project management. And one thing interesting is high accuracy get low precision. :P Sounds contradicting , but a common sense. Case: When you estimate the population, 250,000 in Vancouver is much better in 250,123.
Four dimention of things that affect your estimation: Combination of things you know/ don't know. Simple but True in deep thoughts, apply for everything need planning and managing, such as life. haha. Too much?

Tip for big group project estimation: Palm and Scissors. give the comparable ratio size(1-5)... Can imagine the effectiveness