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| changeDate="2007-05-29T09:20:51.191-0700"> |
| <mainDescription><h3>
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| Agile Estimation
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| </h3>
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| <p>
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| There are three main concepts you need to understand to do agile estimation, see [<a class="elementLinkWithUserText"
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| href="./../../../openup/guidances/supportingmaterials/references.html#COH05" guid="_9ToeIB83Edqsvps02rpOOg">COH05</a>]
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| for more information:
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| </p>
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| <ul>
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| <li>
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| <strong>Estimation of Size</strong> gives a high-level estimate for the work item, typically measured using a
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| neutral unit such as points
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| </li>
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| <li>
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| <strong>Velocity</strong> tells us how many points this project team can deliver within an iteration;
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| </li>
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| <li>
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| <strong>Estimation of Effort</strong> translates the size (measured in points) to a detailed estimate of effort
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| typically using the units of Actual Days or Actual Hours. The estimation of effort indicates how long it will take
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| the team member(s) to complete the assigned the work item(s).
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| </li>
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| </ul>
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| <h4>
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| Estimation of Size
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| </h4>
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| <p>
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| Agile estimation of size is typically done using a relative measure called <strong>points</strong>.&nbsp; The team
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| decides how big a point is, and based on that size, determines how many points each work item is. To make estimation go
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| fast, 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
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| get started, look at 10 or so representative work items, give the smallest the size of one point, and then go through
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| all other work items and give them a relative point estimate based on that point. Note that points are used for
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| high-level estimates, so do not spend too much time on any one item. This is especially true for work items of lower
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| priority, to avoid wasting effort on things that are unlikely to be addressed within the current iteration.
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| </p>
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| <p>
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| A key benefit of points is that they are neutral and relative. Let’s say that Ann is 3 times more productive than Jack.
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| 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,
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| 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,
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| while Jack thinks it can be done in 36 hours. That is fine, they may disagree about the actual effort required to do
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| 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
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| Velocity to determine how much ‘size’, or how many points, the team can take on within an iteration.
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| </p>
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| <p>
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| One project team may say that a work item of a certain size is worth 1 point. Another project team would estimate the
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| same sized work item to be worth 5 points. That is fine, as long as you are consistent within the same project. Make
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| sure that the entire team is involved in assessing size, or at least that the same people are involved in all your size
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| estimates, to ensure consistency within your project. We will see how the concept of velocity will also fix this
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| discrepancy in a point meaning different things to different project teams.
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| </p>
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| <p>
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| You can also use other measures of size, where the most common alternative is Ideal Days. See for example [<a
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| class="elementLinkWithUserText" href="./../../../openup/guidances/supportingmaterials/references.html"
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| guid="_9ToeIB83Edqsvps02rpOOg">COH05</a>] for more information.
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| </p>
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| <h4>
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| Velocity
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| </h4>
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| <p>
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| Velocity is a key metric used for iteration planning. It indicates how many points are delivered upon within an
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| iteration for a certain team and project. As an example, a team planned to accomplish 20 points in the first iteration.
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| At the end of the iteration, they noticed that they only delivered 14 points, so their velocity was 14. For the next
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| iteration, they may plan for fewer points (let’s say 18), since they think they can do a little better than in previous
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| iteration. In this iteration, they delivered 17 points, giving them a velocity of 17.
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| </p>
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| <p>
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| Expect the velocity to change from iteration to iteration. Some iterations go more smoothly than others do, and points
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| are not always identical in terms of effort. Some team members are more effective than others, and some problems end up
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| being harder than others. Also, changes to the team structure, learning new skills, changes to the tool environment,
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| better teaming, or more overhead with meetings or tasks external to the project will all impact velocity. In general,
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| velocity typically increases during the project as the team builds skills and becomes more cohesive.
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| </p>
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| <p>
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| Velocity compensates for differences between teams in terms of how big a point is. Let’s assume that project team Alpha
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| and project team Beta are equally efficient in developing software, and they run the same project in parallel. Team
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| Alpha, however, assesses all work items as being worth 3 times as many points as team Beta's estimates. Team Alpha
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| assesses work item A, B, C, and D to correspond to 30 points, and team Beta estimates the same work items to correspond
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| to 10 points. Both teams deliver upon those 4 work items in the next iteration, giving team Alpha a velocity of 30, and
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| 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
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| plan the next iteration. They both want to take on work item E-H, which team Alpha has estimated to be 30 points, and
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| 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
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| 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
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| big a point is, as long as you are consistent within your team.
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| </p>
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| <p>
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| Velocity also averages out the efficiency of different team members. Let’s look at an example: Let’s assume that Ann
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| always works 3 times as fast as Jack and Jane. Ann will perhaps deliver 9 points per iteration, and Jack and Jane 3
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| points each per iteration. The velocity of that three-person team will be 15 points. As mentioned above, Ann and Jack
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| may not agree on how much effort is associated with a work item, but they can agree on how many points it is worth.
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| Since the team velocity is 15, the velocity will automatically translate the point estimate to how much work can be
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| taken on. As you switch team members, or as team members become more or less efficient, your velocity will change, and
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| you can take on more or fewer points. This does however not require you to change the estimate of the size. The size is
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| still the same, and the velocity will help you to calculate how much size you can deliver with the team at hand for
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| that iteration.
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| </p>
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| <h4>
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| Estimation of Effort
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| </h4>
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| <p>
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| Estimation of Effort translates the size (measured in points) to a detailed estimate of effort,&nbsp;typically using
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| the units of Actual Days or Actual Hours. As you plan an iteration, you will take on a work item, such as detailing,
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| designing, implementing and testing a scenario, which may be sized to 5 points. Since this is still a reasonably big
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| work item, break it down&nbsp;into a number of smaller work items, such as&nbsp;four separate work items for Detailing,
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| Designing, Implementing and Testing the Server, and Implementing and Testing the Client portion of the scenario. Team
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| members are asked to sign up for the tasks, and then detail the&nbsp;estimate of the actual effort, measured in hours
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| or days, for their tasks. In this case, the following actual estimates were done (with person responsible within
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| parenthesis):
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| </p>
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| <ul>
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| <li>
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| Detailing scenario (Ann): 4 hours
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| </li>
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| <li>
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| Designing scenario (Ann and Jack):&nbsp; 6 hours
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| </li>
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| <li>
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| Implementing and Testing Server portion of scenario (Jack): 22 hours&nbsp;
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| </li>
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| <li>
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| Implementing and Testing Client portion of scenario (Ann): 12 hours
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| </li>
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| <li>
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| <strong>Total Effort Estimate for Scenario:</strong> 44 hours
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| </li>
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| </ul>
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| <p>
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| If other people were assigned to the tasks, the estimated actual hours could be quite different. As a result, there is
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| no point doing detailed estimates until you know who will perform the work. Often, some level of analysis and design of
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| the work item needs to take place before a reasonable estimate can be done. Remember that estimates are still
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| estimates, and a person assigned to a task should feel free (and be encouraged) to re-estimate the effort required to
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| complete the task, so we maintain a realistic view of progress within an iteration.<br />
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| </p></mainDescription> |
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