“Humans s**k at estimating in absolute terms but are much better estimating in relative terms.” *
Coarsely put, but a ubiquitous opinion in the Agile community. What’s the evidence for the claim?
Even the Agile Alliance admits it’s weak: “…there is a persistent claim in the Agile community that research in the psychology of planning shows that people fare better at relative than absolute estimation; in fact, the grounding for this claim is at best, tentative.”*
For proof, we’re left with anecdotes. Supposedly, they show how easy and reliable it is to estimate by comparing objects of similar size.
My favorite “proof”: the coconut and the guava. The author claims that it’s easy to use a guava as a reference and say that the coconut is about four times bigger.*
Huh? Many of us from the “high north” don’t find it so easy. Coconuts, yes; but guavas? Four times? Not so much. It’s not like we see them every trip to the 7-Eleven.
Relative estimates require common background knowledge.
That’s a slippery slope. It express beliefs about size. Whatever immediate access I might have to my belief about size, I don’t have the same access to your belief. Do we mean the same thing when we say that a coconut is four times bigger than a guava?
Maybe I’m thinking of volume rather than diameter. To me, the coconut would be 64 times the size of a guava. Or, perhaps you’re thinking of surface area, in which case the difference would be 16 times.
A dialogue might eventually disambiguate the comparison, but the process is not as straight-forward as portrayed. This is especially true when the object is more abstract than a coconut, for instance a user story.
Want to plan your next sprint? Avoid the pitfalls of relative estimates. Rely instead on absolute numbers such as Earned Schedule’s duration estimate.
It’s an absolute number based on absolute numbers. It uses current performance to estimate finish date. And, it can be compared to allowances for uncertainty—again, specific numbers.
Is it better for planning your next sprint? Absolutely!
* For references, see below. Follow ProjectFlightDeck on LinkedIn. For videos on how to use Earned Schedule, see EarnedScheduleAcademy on YouTube. And, when you’re ready, sign up for ProjectFlightDeck Express.
References:
http://chase-seibert.github.io/blog/2016/05/13/agile-points-vs-hours.html
https://www.agilealliance.org/glossary/relative-estimation/#q=~(filters~(postType~(~'page~'post~'aa_book~'aa_event_session~'aa_experience_report~'aa_glossary~'aa_research_paper~'aa_video)~tags~(~'relative*20estimation))~searchTerm~'~sort~false~sortDirection~'asc~page~1) |
