Distinguish between estimates, targets, and commitments.
When you’re asked to provide an estimate, determine whether you’re supposed to be estimating or figuring out how to hit a target.
When you see a single-point “estimate,” ask whether the number is an estimate or whether it’s really a target.
When you see a single-point estimate, that number’s probability is not 100%. Ask what the probability of that number is.
Don’t provide “percentage confident” estimates (especially “90% confident”) unless you have a quantitatively derived basis for doing so.
Avoid using artificially narrow ranges. Be sure the ranges you use in your estimates don’t misrepresent your confidence ...