Agile planning and the story points approach - Part 02

In the last post post of this series, we have discussed an Agile project management estimation technique, useful when planning in a context of high uncertainty.
The estimation of tasks' sizes using story points.

The concept at the core of the evaluation by story points technique is to estimate activities’ related efforts, instead of activities’ actual durations. Then, as the project progresses, we will be able to transform points into time, using performances achieved in previously accomplished activities.

In this post, we will talk about why this kind of approach works. We will go a little more in-depth, giving evidence of some common pitfalls and solving doubts that typically emerge when approaching this technique.

Why it does work

Relative estimations are easier than absolute ones

It is much easier estimate something comparing it to what we already know, instead of making up a precise quantification out of the blue. You can get evidence of this claim at almost any moment in your life, in which you have to explain something to someone. What would you rather say “Hey Jack, do you know that Tom is 1.76 meters high and weights 97 Kilograms?” or “Hey Jack, do you know that Tom is almost as high as me, and weights more or less the same as Pete?”

Velocity is the great equalizer
The team could estimate its velocity as the average of the number of story points achieved in the last N iterations. It would be pretty useless for the team committing to the implementation of 25 story points in the next iteration if the average velocity achieved in the last 5 iterations is 10. The velocity concept and the averaging operation will smooth out the effect of any unforeseen problem (or luck) that the team may have encountered in performing the job.

Agile teams are, by definition, multidisciplinary teams
The presence of people with many competencies and skills in the team helps in achieving meaningful and reliable estimations. The number of points for one story should not be decided just by an individual. It should come from negotiations and confrontations between all the team members. This approach leads us to the next principle.

The team, not the individuals, commits to a velocity
The work to do, in an Agile team, should be shared by many team members. It is all right to have a specialist in software testing, as long as he/she won’t take care of all the testing. The most skilled team member would probably take care of the more delicate tasks in its specialization domain, but he/she have not to exclude other team members from this kind of activities. Just, in this case, the team can commit to a common objective. Otherwise, you won’t have an Agile team; you will end up with a bunch of professionals, trying to deliver something in their specialization domain without getting in the way of other people.

To have it working

The team composition should be fixed
Team velocity is based on estimations of task’s size and execution performances. Usually, some iterations are necessary to reach convergence and give reliable evaluations. 

As you may imagine, if the team’s composition is frequently changed, there is no way to reach a condition of stability.

Agile teams must be made up of T-people
Since in an Agile teams, estimations are made collectively, and tasks of the same kind are shared among different resources, you need the so-called T-people. That is to say, people who are extremely proficient in a given area of the project, but sufficiently skilled to be helpful in many others.  

You need ants, not tigers
Agile teams must be made up of average performers, who care more about the team than themselves. Do not directly jump to conclusions; you do not need dumb people. You need a well-balanced set of smart people, with comparable performances. Believe me, you do not want to have lone rangers or superstars in an Agile team.

You have to make a transition from the standard project management paradigm
Obviously, if the team has to commit on an objective to be reached in an iteration, all the members should have a certain degree of freedom in selecting the target itself. This approach requires a particular shift in the project management paradigm.

In an Agile team, the project manager must delegate more than in a standard environment. The team must be free to select the tasks to perform in the iteration, balancing the stakeholders’ requirements with the team’s capabilities.

Common pitfalls

Story points have no meaning per se

Story points define the size of an activity related to the other ones; do not try to convert them to man/hours and to redefine activities’ durations. Story points conversion is a dangerous road to walk by. Work with story points and use velocity.

Do not change estimation of past stories
Sometimes you may be tempted to change the points size of some features; maybe because you become aware that a task is much more difficult (or easy) to perform than previously expected. In such a case resist the urge to change the task’s size. Remember, velocity is the great equalizer. The story points and velocity system will take care of such eventualities. If the task to perform is much more complicated (or simple) than expected, you will experience a physiological velocity increase (or decrease) in next iterations.

Different teams’ velocities are meant to be different
Once I hear a project manager saying “Team A is performing better than team B; in fact, team A achieved a velocity 5 points greater than the one obtained by team B.” Dead wrong. Different teams, with different tasks and different estimations probably will have different velocities, but this means nothing. Remember that story points have just a comparative meaning and are subjective from team to team. Do not compare teams’ performances basing on their velocities.

A last comment

If you think that an agile planning approach is not a silver bullet, you are perfectly right.

Agile planning is an extremely useful tool, that should be present in every project manager’s tool bag; nonetheless, you have to select carefully, which projects could benefit from it.

Furthermore, do not forget that also the business environment in which the project lives should be ready to adopt such an approach.

Quest' opera è distribuita con licenza Creative Commons Attribuzione - Non commerciale - Non opere derivate 3.0 Unported.

Agile planning and the story points approach - Part 01

We begin with this post a series dedicated to the exploration of a well-known agile planning techniques. The story points estimation method.
In this post, we will introduce some fundamental concepts with the aid of a very simple example. In subsequent posts, we will dive a little more into depth, discussing why this approach works, exposing common pitfalls and, hopefully, answering some doubts.

Let us try a little experiment.

In the middle of a field, there are three swimming pools

• Swimming pool #1    2 meters long, 1 meter wide and 1 meter deep.
• Swimming pool #2    4 meters long, 1 meter wide and 1 meter deep.
• Swimming pool #3    3 meters long, 2 meters wide and 1 meter deep.

Imagine you have to empty all the three pools, one after the other, starting with the smaller pool and finishing with the bigger one, using just a bucket. Every time you pull a bucket of water out of a pool, you must pour it in a well, at one corner of the field. The bucket is known to bear a small defect that will slow down the tasks’ execution, without impeding it. You do not have any clue about what the defect is.

Could you give me an estimate of the time you will need to perform the three tasks?

No. You cannot.

You cannot, because I have not been fair to you. I deliberately have hidden some information that you would need, in order to construct a reliable estimation.

• You do not know how big the bucket is. It may be the size of a mug or as big as a gasoline tank.
• You do not know which the bucket’s defect is and how this will affect the tasks’ execution.
• You do not know how far the well is. You know that the well is at one corner of the field, but you ignore how big is the area. The field could be a 10x10 meters square, or it may be as big as a football court.

A guess about the tasks’ execution time would probably be so much erratic, or its standard deviation of such a magnitude, that the estimation itself would end up to be utterly useless.

Points instead of time

Let us work with what we have. 

We know that swimming pool #2 is twice the size of swimming pool #1, and that swimming pool #3 is three times the size of swimming pool #1. 

Defined X the time required to empty Swimming pool #1, we can state as 2X the time required to empty Swimming pool #2 and 3X the time required to empty Swimming pool #3.

Since we do not have any clue about the value of X, we drop it in our estimations. 

We define that 

• Emptying Swimming pool #1 (activity #1) is 1 a point activity.
• Emptying Swimming pool #2 (activity #2) is a 2 points activity.
• Emptying Swimming pool #3 (activity #3) is a 3 points activity.

Ok, but how much is a point? Velocity is the key

At this point, we can start emptying Swimming pool #1. I have decided to help you in the job. You do not have to thank me for this; I love emptying swimming pools with a broken bucket.

After a very hard work, we realize that the activity has taken us 1 day, or, that is equivalent, we have a velocity of 1 points/days. We can now estimate, using the concept of velocity, activity #1 to be a 2 days activity and activity #3 to be a 3 days activity.

Propagating and refining the estimation

The next day you start emptying Swimming pool #2. Yes, you. 

I feel a little sick and tired of buckets and water. After three days of hard work, you finish this activity too. It has taken longer than expected since I did not help you till the morning of the third day and that, probably, you felt a little tired from the previous days of hard work.

How long will take finish activity #3?
It had been initially estimated as a 3 days activity (3 points with a velocity of 1 points/days), but our velocity has changed. Using the last activity velocity (0.67 points/days), we can now re-estimate activity #3 as a 4.5 days activity. 

This approach may work, but I think it is not a good idea. I will help you in activity #3 and do not forget that tomorrow is Friday. We will have two days to rest. 

Let us estimate our velocity as the mean of the velocities achieved in the last two activities, obtaining a velocity of 0.83 points/days and an estimation of activity #3 ‘s duration of 3.5 days.

Conclusions

In a context of high uncertainty, estimate an activity’s duration could be a daunting task. We could do our best but sometimes, as Christopher Cross would say, it is not enough. An estimation would be so much erratic, or its standard deviation so wide, that the estimation itself would be completely useless.

Instead of guessing and correcting, we could rely on an agile project management concept. 

The concept is to estimate activities’ relative efforts, instead of activities’ absolute durations. 

Then, as the project progresses, we will be able to transform points into time, using performances achieved in previously accomplished activities.

The more we proceed in a project, the more the estimations of activities' durations become accurate, since averaging velocities smooth out particular events, which could have affected, positively or negatively, our performances.

Doubts

In this post, we have presented a widely used agile planning technique, the estimation of activities’ efforts by (story) points. We have introduced the approach by mean of a simple example, and we have investigated how it works.

In the next post of this series, we will talk about why this kind of approach works. We will go a little more in depth, removing some simplifications that I have introduced for the sake of simplicity. We will give evidence to some common pitfalls, and we will try to solve doubts that typically emerge when first approaching this technique.

Quest' opera è distribuita con licenza Creative Commons Attribuzione - Non commerciale - Non opere derivate 3.0 Unported.