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In all of the workplaces that I've been to so far, there is a strong conviction that estimating the work in the story points leads to the more accurate estimations than using old-school work-hours. This belief seems to be also wide-spread in the various online resources (websites) related to the topics of planning the work.

Many of my supervisors as well as my current colleagues hold this opinion too. However when approached about this point they fail to point me to any source nor evidence that would support this view.

Is there any evidence that estimating the work in story points leads to more accurate estimations than estimating the work in hours?

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  • Most workplace practices and policies are not based upon academic research or publications, but upon personal experience of individuals and organizations, passed along over time through oral traditions, shared experiences, evolution, case-studies of places that succeeded/survived and adopting what they tried, on the job training, etc. - which is rarely ever published. If you try to go at it from theory-first, or data-driven, or "evidence-based", you will generally be very annoyed to find that most workplaces don't work that way at all - not even a little bit.
    – BrianH
    Commented Sep 4, 2019 at 15:59
  • @BrianH thanks for the comment BrianH. While I am aware of how most of the workplaces work (though I would argue that more and more workplaces are aiming to be more data-driven) that doesn't answer the question posted by me. I am not annoyed by estimating my work in story points, I just want to find out is there any truth to it.
    – kukis
    Commented Sep 4, 2019 at 16:03
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    I'm voting to close this question as off-topic because it is about Software Engineering not navigating the workplace.
    – IDrinkandIKnowThings
    Commented Sep 4, 2019 at 17:17
  • Estimating work as "story points" or even "hours" is prone to all manner of issues. The most common is "who is doing this work?" After that comes "How many meetings are going to interrupt that work?" Which is better? Neither.
    – Julie in Austin
    Commented Sep 4, 2019 at 17:39
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    @kukis Also consider asking this in the Project Management SE: pm.stackexchange.com (Where they deal with all kinds of projects, not necessarily just 'software' projects.)
    – seventyeightist
    Commented Sep 4, 2019 at 21:05

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I don't believe so. Story points reduce the accuracy of estimations because they are by nature ballpark estimates. Its best not to try to get too granular when estimating size, anyway, because most of the time it cant be accurately determined ahead of time. I'm guessing your employer found time-based estimates to be unreliable due to inaccuracy, and are able to accept the inaccuracy of size estimates because they don't claim to be a definitive mapping between size and time spent. The inexact nature is baked into the methodology rather than being a metric by which to value them.

In short, I think story points just make the ambiguity of story-level delivery dates more palatable to management. I think by their very nature they are not more accurate, but easier to accept. When a story is estimated at 3 days and it gets delivered in 5, it suggests that the system is inaccurate for estimates or that the development team is under-performing. When a story is estimated at size 3 and it gets delivered in 5 days its fine because nobody ever claimed it would be done in 3 days in the first place.

Plenty of teams in my organization are moving away from estimations at the story level entirely. Some teams only use a simplified 1-3-5/small-medium-large estimate that they use only to determine if a story might be big enough to be broken down into smaller stories. Really story size/time estimates should be used as a metric on the dev team level, not the PO and stakeholder level. Management should only rely on committed deliverables for visibility unless they have a particularly keen interest on a particular story or feature. Size/time estimates should not be considered a commitment, just an estimation. The sprint itself is the commitment.

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    There's a difference between accuracy and precision. It could be argued that "story points" are more "accurate" because they're less "precise" - it's much easier to hit the target if it's got a larger area... Accuracy vs Precision
    – brhans
    Commented Sep 4, 2019 at 18:16
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In my experience, there is no one size that fits all. There are teams that struggle with estimating story points right, and then there are also teams that under-budget and overshoot the hours.

IMO, it all boils down to the kind of work you do, whether your work permits writing concise stories or not, which have defined acceptance criteria, the overall familiarity of the team with either methodology, and so on.

So, to answer your question:

Is there any evidence that estimating the work in story points leads to more accurate estimations than estimating the work in hours?

No there isn't, because that question is at the heart of hours vs story points debate that many organizations face, as for some, an estimate in hours is more easily dollar convertible than an estimate in story points. You will just find proponents claiming victory for whichever side of the fence they are on.

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