The first key mistake of software estimation in industry is that we rarely talk about confidence (e.g “I’m 50% confident it’ll be shipped in 5 hours, but 99% confident it’ll ship before end of week”). The fact that this is not part of planning means it’s often not part of the conversation and that we seldom think about estimation as a tuple of value and confidence.

The second key mistake is forgetting that estimates (at least in software) are an upper bound. So high estimates are often “better”.