Software Estimation: Demystifying the Black Art (Best Practices (Microsoft))

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.