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| <mainDescription><h3> |
| Agile Estimation |
| </h3> |
| <p> |
| There are three main concepts you need to understand to do agile estimation: |
| </p> |
| <ul> |
| <li> |
| <strong>Estimation of Size</strong> gives you a high-level estimate for the work item, typically measured using a |
| neutral unit such as points |
| </li> |
| <li> |
| <strong>Velocity</strong> tells us how many points this project team can deliver within an iteration; |
| </li> |
| <li> |
| <strong>Estimation of Effort</strong> translates the size (measured in points) to a detailed estimate of effort |
| typically using the units of Actual Days or Actual Hours. The estimation of effort indicates how long it will take |
| the team member(s) assigned to the work item to do the work. |
| </li> |
| </ul> |
| <h4> |
| Estimation of Size |
| </h4> |
| <p> |
| Agile estimation of size is typically done using a relative measure called <strong>points</strong>.&nbsp; You decide |
| how big a point is, and based on that size, you determine how many points each work item is. To make estimation go |
| fast, you want to use only full points, 1, 2, 3, 5, 8, and so on, rather than fractions of a point, such 0.25, or 1.65 |
| points. To get started, look at 10 or so representative work items, give the smallest the size of one point, and then |
| go through all other work items and give them a relative point estimate based on that point. Note that points are used |
| for high-level estimates, so do not spend too much time on any one item. This is especially true for work items of |
| lower priority, since you would then waste effort on things that are unlikely to be addressed within the current |
| iteration. |
| </p> |
| <p> |
| A key benefit of points is that they are neutral and relative. Let’s say that Ann is 3 times more productive than Jack. |
| If Ann and Jack agree that work item A is worth 1 point, and they both think work item B is roughly 5 times as big, |
| they can rapidly agree that work item B is worth 5 points. Ann may however think work item B can be done in 12 hours, |
| while Jack thinks it can be done in 36 hours. That is fine, they may disagree about the actual effort required to do |
| it, but we do not care at this point in time, we only want the team to agree on the relative size. We will later use |
| Velocity to determine how much ‘size’, or how many points, the team can take on within an iteration. |
| </p> |
| <p> |
| One project team may say that a work item of a certain size is worth 1 point. Another project team would estimate the |
| same sized work item to be worth 5 points. That is fine, as long as you are consistent within the same project. |
| You&nbsp;want to make sure that the entire team is involved in assessing size, or at least that the same people are |
| involved in all your size estimates, to ensure consistency within your project. We will see how the concept of velocity |
| will fix also this discrepancy in a point meaning different things to different project teams. |
| </p> |
| <p> |
| You can also use other measures of size, where the most common alternative is Ideal Days. See for example [<a class="elementLinkWithUserText" href="./../../../openup_basic/guidances/supportingmaterials/references,_9ToeIB83Edqsvps02rpOOg.html" guid="_9ToeIB83Edqsvps02rpOOg">COH05</a>] for more information. |
| </p> |
| <h4> |
| Velocity |
| </h4> |
| <p> |
| Velocity is a key metric used for iteration planning. It indicates how many points are delivered upon within an |
| iteration for a certain team and project. As an example, a team may plan for taking on 20 points in the first |
| iteration. At the end of the iteration, they noticed that they only delivered upon 14 points, their velocity was hence |
| 14. For the next iteration, they may plan for fewer points, let’s say 18 points, since they think they can do a little |
| better than in previous iteration. In this iteration, they delivered 17 points, giving them a velocity of 17. |
| </p> |
| <p> |
| You should expect the velocity to change from iteration to iteration. Some iterations go smoother than others, and |
| points are not always identical in terms of effort. Some team members are more effective than others, and some problems |
| end up being harder than others. Also, changes to the team structure, learning new skills, changes to the tool |
| environment, better teaming, or more overhead with meetings or tasks external to the project will all impact velocity. |
| In general, velocity typically increases during tha project as the team builds skills and becomes more cohesive. |
| </p> |
| <p> |
| Velocity compensates for differences between teams in terms of how big a point is. Let’s assume that project team Alpha |
| and project team Beta are equally efficient in developing software, and they run the same project in parallel. Team |
| Alpha, however, assesses all work items as being worth 3 times as many points. Team Alpha assesses work item A, B, C, |
| and D to correspond to 30 points, and team Beta estimates the same work items to correspond to 10 points. Both teams |
| deliver upon those 4 work items in the next iteration, giving team Alpha a velocity of 30, and team Beta a velocity of |
| 10. It may sound as if team Alpha is more effective, but let’s look at what happens when they plan the next iteration. |
| They both want to take on work item E-H, which team Alpha has estimated to be 30 points, and team Beta as normal has |
| estimated to be 1/3 as many points, or 10 points. Since a team can typically take on as many points as indicated by |
| their velocity, they can both take on all of E-H. The end result is that it does not matter how big a point is, as long |
| as you are consistent within your team. |
| </p> |
| <p> |
| Velocity also averages out the efficiency of different team members. Let’s look at an example; Let’s assume that Ann |
| always works 3 times as fast as Jack and Jane. Ann will perhaps deliver 9 points per iteration, and Jack and Jane 3 |
| points each per iteration. The velocity of that 3-person team will be 15 points. As mentioned above, Ann and Jack may |
| not agree on how much effort is associated with a work item, but they can agree on how many points it is worth. Since |
| the team velocity is 15, the velocity will automatically translate the point estimate to how much work can be taken on. |
| As you switch team members, or as team members become more or less efficient, your velocity will change, and you can |
| hence take on more or less points. This does however not require you to change the estimate of the size. The size is |
| still the same, and the velocity will help you to calculate how much size you can deliver upon with the team at hand |
| for that iteration. |
| </p> |
| <h4> |
| Estimation of Effort |
| </h4> |
| <p> |
| As you plan an iteration, you will take on a work item, such as detail, design, implement and test a scenario, which |
| may be sized to 5 points. Typically you at this time break down this still reasonably big work item into a number of |
| smaller work items, such as 4 separate work items for Detailing, Designing, Implementing and Testing Server portion, |
| and Implementing and Testing Client portion of the scenario. You would now do a detailed estimate of the actual effort, |
| measured in hours or days, associated with each of those 4 tasks. This estimate should be done by the person assigned |
| to do the task. In this case you may assign the following actual estimates (with person responsible within |
| parenthesis): |
| </p> |
| <ul> |
| <li> |
| Detailing scenario (Ann): 4 hours |
| </li> |
| <li> |
| Designing scenario (Ann and Jack):&nbsp; 6 hours |
| </li> |
| <li> |
| Implementing and Testing Server portion of scenario (Jack): 22 hours&nbsp; |
| </li> |
| <li> |
| Implementing and Testing Client portion of scenario (Ann): 12 hours |
| </li> |
| <li> |
| <strong>Total Effort Estimate for Scenario:</strong> 44 hours |
| </li> |
| </ul> |
| <p> |
| If other people would be assigned to the tasks, the estimated actual hours could be quite different. There is hence no |
| point doing detailed estimates until you know who will do the work, and what actual problems you will run into. Often, |
| you have to do some level of analysis and design of the work item before you can come up with a reasonable estimate. |
| Remember that estimates are still estimates, and a person assigned to a task should feel free (and be encouraged) to |
| re-estimate the effort required to complete the task, so we have a realistic view of progress within an |
| iteration.<br /> |
| </p></mainDescription> |
| </org.eclipse.epf.uma:ContentDescription> |