I’m an enormous proponent of estimating in story factors. (You will get a full overview of methods to use story factors within the video above or from studying What Are Story Factors.)
In all of my coaching and writing about story factors, person tales, planning poker, and agile estimating, I’ve been fairly adamant that story factors are about effort. I’ve additionally defined that we speak about that effort by way of how lengthy it would take to complete as a result of that’s 1) how we naturally take into consideration the hassle concerned to do a job and a couple of) how we will reply questions on when a venture will be delivered.
However once I say that agile story factors are about effort and that effort is measured in time, it doesn’t imply groups ought to say, “One story level equals eight hours.” Nor ask, “One story level is what number of hours?” Equating story factors to a set variety of hours is a foul concept. Don’t do it.
Equating hours to story factors obviates the first purpose to make use of story factors within the first place: Story factors are useful as a result of they permit workforce members who carry out at totally different speeds to speak and estimate the quantity of labor collaboratively.
Story factors work as a result of they’re relative models of measure, whether or not you might be estimating with a set of playing cards, T-shirt sizing, or the Fibonacci collection. (For extra on why relative estimates are important, learn The Fundamental Purpose to Use Story Factors.)
Agile Estimation Is Summary On Objective
Through the use of story factors, agile groups with builders who work at totally different speeds can agree on estimates. A senior developer would possibly be capable to knock out a sure product backlog merchandise in 8 hours, and a extra junior developer would possibly take 16 hours to do the identical work, however they’ll each agree that it’s a 1-point story.
With that settlement in place, they’ll take a look at one other story and agree that it’s going to take twice as a lot effort, so it needs to be value two factors. Or it’s 5 occasions as a lot effort, and needs to be 5 factors.
Let’s take a look at an instance. For simplicity, let’s assume the workforce has two members:
Celebrity is extra skilled, expert, and educated than Junior. This results in Celebrity being 4 occasions extra productive than Junior. Any job that Junior can full in 4 hours, Celebrity can full in a single.
This workforce of two has a mean velocity of 25 story factors per dash. This results in them planning to finish the next product backlog objects within the coming dash.
| Photographs | factors |
|---|---|
| A | 10 |
| B | 5 |
| C | 5 |
| D | 5 |
As a result of Celebrity is 4 occasions extra productive than Junior, Celebrity will be capable to full 4 occasions as many factors within the dash. Which means Celebrity will full 20 and Junior 5 of the 25 factors deliberate within the dash.
Junior can work on any of the five-point objects and efficiently full it in the course of the dash. Let’s assume Junior chooses merchandise D. That leaves Celebrity with objects A, B, and C as proven beneath.
| Gadgets | Factors | Celebrity | Junior |
|---|---|---|---|
| A | 10 | X | |
| B | 5 | X | |
| C | 5 | X | |
| D | 5 | X | |
| Complete | 20 | 5 |
So what can we inform somebody who asks, “What number of hours does it take to finish one level?”
If we assume this instance is a 1-week, 40-hour dash, there are 3 potential solutions.
- Celebrity labored 40 hours and delivered 20 factors. Due to this fact, one level takes two hours of labor.
- Junior labored 40 hours and delivered 5 factors. Due to this fact 1 level takes 8 hours. Word that Junior’s variety of hours per level is 4 occasions that of Celebrity. This corresponds to the preliminary assumption that Celebrity is 4 occasions as productive.
- Collectively, they labored 80 hours and accomplished 25 factors. Due to this fact, 1 level takes 3.2 hours (80/25).
You may see from this instance that there is no such thing as a equivalence between factors and hours. You can not say one level equals such-and-such variety of hours. For Celebrity, some extent is 2 hours, for Junior it’s 8 hours, and for the workforce it’s 3.2 hours.
But when the workforce doesn’t hearken to me, they usually outline some extent as being equal to three.2 hours, Junior and Celebrity will be unable to agree on estimates as a result of they produce such dramatically totally different leads to 3.2 hours.
With story factors, alternatively, everybody can speak about and estimate the work, and the estimate might be correct regardless of which developer works on the story. On this approach, story factors are nonetheless about effort, however the period of time it takes to finish every level will not be mounted on the identical quantity for all workforce members.
Equating Story Factors to Hours Complicates Pondering
The second downside with equating story factors to a set variety of hours is that workforce members not assume abstractly. If somebody instructs workforce members that one level equals eight (or any variety of) hours, the advantages of estimating in an summary however comparatively significant unit like story factors are misplaced.
Once you attempt as an alternative to transform story factors to hours, you all of the sudden provoke an hours-to-story-points calculator in each workforce member’s head. When instructed to estimate the hassle required for a narrative with a particular time per level in thoughts, the workforce member will mentally estimate first utilizing the variety of hours after which convert that estimate to factors.
So in our first instance, a senior developer who may full a narrative in eight hours would name a product backlog merchandise a one-point story (8/8=1 level). A junior developer who would possibly take sixteen hours to do the work would name that very same product backlog merchandise a two-point story (16/8=2 factors). Mathematically, they’d each be proper, however they’d be miles away from one another by way of agreeing on an estimate.
When story factors are tied to a sure variety of hours, story factors are not relative. Story level estimation turns into totally depending on who’s doing the work.
If somebody in your organization desires to begin translating story factors to hours, simply cease calling the models factors and use the label of hours or days as an alternative. Calling them factors after they’re actually simply hours introduces pointless complexity (and loses one of many primary advantages of factors: workforce members with totally different talent ranges have a standard unit of measure).
The Relationship Between Story Factors and Hours
So is there a relationship of agile story factors to hours? Sure. Suppose for some purpose you could have tracked how lengthy each one-story-point story took to develop for a given workforce, and saved it in a story-points-to-hours desk. If you happen to graphed that information you’ll have one thing that might appear like this:
This exhibits that some tales took extra time than others and a few tales took much less time, however total the period of time spent in your one-point tales takes on the form proven.
Now suppose you had additionally tracked the period of time spent on two-point person tales. Graphing that information as nicely, we’d see one thing like this:
Ideally the two-point tales would take twice so long as the one-point tales. That’s unlikely to be precisely the case, in fact. However a workforce that does a great job of estimating might be sufficiently shut for dependable plans to be constructed from their estimates based mostly on their common workforce velocity.
What these two figures present us is that the connection between factors and hours is a distribution. One level equals a distribution with a mode of x, two factors equals a distribution with a mode of 2x, and so forth.
By the way in which, discover that I’ve drawn the distributions of one- and two-point tales as having overlapping tails. It is vitally doubtless that a few of the most time-consuming one-point backlog objects take longer than a few of the shortest two-point objects. In spite of everything, no workforce can estimate with good perception, particularly on the story level stage.
So, whereas the tails of the one- and two-point distributions will overlap, it could be terribly unlikely that the tails of, say, the one- and thirteen-point distributions will overlap (I’m assuming right here that you’re utilizing a modified fibonacci sequence in your story factors, however you could possibly use any set of numbers).
Why This Issues
Some agile groups outline the connection between story factors and hours as an equivalence. That’s one level equals some variety of hours. And by extension, two factors is twice that variety of hours and so forth.
This can be a mistake, and makes factors irrelevant as a result of they merely turn into a translation of hours. Mapping story factors to hours makes it unattainable for workforce members who produce their work at totally different charges to agree on estimates. Groups that convert Jira story factors to hours by a set equivalence (corresponding to one level equals eight hours) will find yourself with inaccurate plans.
These issues recede when groups perceive that the connection between story factors and hours is a distribution. That’s, one-point objects take from x to y hours. And two-point backlog objects take from about 2x to 2y hours.
So How Many Hours Is a Level?
When doing agile estimating, changing story factors to hours by a easy one level equals x hours formulation will lead to deceptive solutions which might be overprecise. When stakeholders inform us issues like, “translate all these loopy agile fibonacci story factors to hours so I do know what it means” they need merely to know methods to interpret the story factors we inform them.
We will present that understanding utilizing velocity. Suppose stakeholders need to know the way lengthy a 5-point backlog merchandise will take and that our workforce’s common velocity is 20. We will inform the stakeholders that the five-point merchandise is about one-fourth of the workforce’s whole capability for the dash.
Going Additional
If you wish to make sure you perceive story factors, I counsel this on-demand video course on Estimating with Story Factors.
