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How does a "bad estimate" cause a project to be delayed? I think this type of wording is part of what causes animosity in the industry about this topic. Estima

How does a "bad estimate" cause a project to be delayed? I think this type of wording is part of what causes animosity in the industry about this topic. Estimates are not called "promises" for a reason, and any attempt at treating them that way will result in failure. Software estimates are notoriously hard to get right and it's not uncommon for them to be wrong by several orders of magnitude, and this effect is magnified for bigger estimates/work. Any decent project plan needs to assume this is the case, and it needs to be continually refined as work progresses and the accuracy of "estimated remaining work" gets higher as the problem is better understood. The worst project plans are the ones that take the initial estimates and use those as delivery dates, but I'd classify that as a "bad plan", not "bad estimate".

JamesBarney 6y ago
A bad estimate causes a delay to the project schedule (in the sense the schedule is delayed, not in the sense the software takes longer to write) . It's not the same kind of delay, but to many stakeholders it's perceived as the same kind of delay. > Estimates are not called "promises" for a reason, and any attempt at treating them that way will result in failure. So management 95% of the time treats estimates as commitments. What they are going to do with the numbers you give them is promise upper management or clients "feature x will be done by y". As engineers we have two options, scream until we're blue in the face "that was an estimate not a commitment" or just give them a commitment and call it an estimate. You're right software estimation is hard, but the really bad estimates I've seen (> 100% over) were due to a combination of dysfunctional organizations, lack of estimating skill, and an organization that didn't put effort into making sure it's estimates were right.
thr0w__4w4y 6y ago
> Software estimates are notoriously hard to get right and it's not uncommon for them to be wrong by several orders of magnitude OK now hold on there just a sec... I've seen estimates off by 20%, 50%, even 100%. I'm sure there are estimates that have been off by 500% (I'd hate to dig into why). But "several orders of magnitude" is something like 10,000x -100,000x. Hopefully that is just extreme hyperbole, but honestly in the context of discussing estimates, it seems particularly out of place.
arcticbull 6y ago
Bad estimates can cause shipping delays when cross-functional or inter-dependent work ends up in day-for-day slip because not all work is parallizable. The only time a bad estimate doesn't cause a delay is when it's "single-threaded" and the long pole.

JamesBarney 6y ago

A bad estimate causes a delay to the project schedule (in the sense the schedule is delayed, not in the sense the software takes longer to write) . It's not the same kind of delay, but to many stakeholders it's perceived as the same kind of delay. > Estimates are not called "promises" for a reason, and any attempt at treating them that way will result in failure. So management 95% of the time treats estimates as commitments. What they are going to do with the numbers you give them is promise upper management or clients "feature x will be done by y". As engineers we have two options, scream until we're blue in the face "that was an estimate not a commitment" or just give them a commitment and call it an estimate. You're right software estimation is hard, but the really bad estimates I've seen (> 100% over) were due to a combination of dysfunctional organizations, lack of estimating skill, and an organization that didn't put effort into making sure it's estimates were right.

thr0w__4w4y 6y ago

> Software estimates are notoriously hard to get right and it's not uncommon for them to be wrong by several orders of magnitude OK now hold on there just a sec... I've seen estimates off by 20%, 50%, even 100%. I'm sure there are estimates that have been off by 500% (I'd hate to dig into why). But "several orders of magnitude" is something like 10,000x -100,000x. Hopefully that is just extreme hyperbole, but honestly in the context of discussing estimates, it seems particularly out of place.

arcticbull 6y ago

Bad estimates can cause shipping delays when cross-functional or inter-dependent work ends up in day-for-day slip because not all work is parallizable. The only time a bad estimate doesn't cause a delay is when it's "single-threaded" and the long pole.