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Agile Estimation
by
Kshitij Agrawal
Agenda
Velocity
Planning Poker
Agile Estimation - Tips and techniques
Agile Estimation – Ideal days vs. story points
Estim...
What is Estimate?
 Estimate is an informed guess and it’s different from actual.
 There is no such thing as “accurate es...
Estimation – Reasons for Variance
No Historic Data
Unclear Requirements
Lack of Domain or
technical knowledge Scope Creep
...
Estimation
When people are pushed for accurate estimate, they just add lot of contingency to save themselves.
Estimation advantages and Tips
Advantages
 Estimate helps in understanding the viability.
 Estimate helps in project pla...
Traditional and agile measures of size
Traditional
Measures of Size
Lines of Code
Function Point
Agile
Measures of Size
Id...
Estimating in Ideal Days
 Ideal Time is - How long something would take if
 It’s all you work on
 You have no interrupt...
Relative Estimation
Small Medium Large
Can you divide mangoes from this huge pile into three boxes based on size?
Do you n...
Estimating in Story Points
 Story Point is relative size / “bigness” of task
 Depends on “how hard it is”
 Depends on “...
Comparing Approaches – Ideal Days
 Ideal days can force companies to confront time wasting activities
 Ideal days are ea...
Comparing Approaches – Story Points
 Story points help drive cross-functional behavior. Whole team irrespective of specia...
Tips & Techniques for Estimation
 Estimates are shared – estimation should be done collaboratively by team – by the
peopl...
Agile Estimation - How Much Effort?
 A little effort helps a lot
 A lot of effort only helps a little more
Accuracy
Effo...
Agile Estimation – Using the right scale
 Can you decide whether given story is a one point story OR a two points story?
...
Agile Estimation – Just in time
Each of the priority items
has a size estimate in story
point or ideal days
Very large ite...
Planning Poker
 Planning poker is a variation of Delphi method.
 An iterative approach to estimating
The key steps are:
...
Planning Poker example
Estimators Round 1 Round 2
Tara 3 5
Bala 8 5
Joju 2 5
Chris 5 8
Ref: www.PlanningPoker.com
Why does Planning Poker work?
 Those who will do the work, estimate the work
 Everyone’s opinion is heard – helps in buy...
Velocity
 Velocity is a measure of a team’s rate of progress.
 Sum of story points assigned to each completed user story...
Thank You 
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Agile estimation

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An introduction to agile estimation

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Agile estimation

  1. 1. Agile Estimation by Kshitij Agrawal
  2. 2. Agenda Velocity Planning Poker Agile Estimation - Tips and techniques Agile Estimation – Ideal days vs. story points Estimation Basics – What and why
  3. 3. What is Estimate?  Estimate is an informed guess and it’s different from actual.  There is no such thing as “accurate estimate”.  Variance is a reality so let’s accept it!  How long will it take to read 500 page thick book?  How long will it take to drive to a particular city or state?  How long will it take for you to create a sand house/castle like this: “As the size and complexity increases, it becomes almost impossible to give a precise estimate”
  4. 4. Estimation – Reasons for Variance No Historic Data Unclear Requirements Lack of Domain or technical knowledge Scope Creep Non-developer Estimating Variance Just for an illustration, imagine each of the variance source causes 30% variance then cumulative range of variance could be: - “1 – 1.3*1.3*1.3*1.3*1.3” = “1 – 3.7” => 370% variance If can’t estimate accurately then why estimate? Some Lean/Kanban experts even believe “Estimate is overhead. It’s waste.”
  5. 5. Estimation When people are pushed for accurate estimate, they just add lot of contingency to save themselves.
  6. 6. Estimation advantages and Tips Advantages  Estimate helps in understanding the viability.  Estimate helps in project planning and execution.  Estimate helps in prioritization.  It provides another opportunity to collaborate and get better understanding of requirements and design. Tips  Estimate in range rather than giving a single figure.  Estimate is NOT same as commitment so modify it when you learn anything new.  Any estimate is as good as its underlying reasoning and assumptions.  Historic data is good for estimation.  Current Data is even better and that’s where Agile focus. “It’s better to be roughly right than precisely wrong.” - John Maynard Keynes
  7. 7. Traditional and agile measures of size Traditional Measures of Size Lines of Code Function Point Agile Measures of Size Ideal Days Story Points
  8. 8. Estimating in Ideal Days  Ideal Time is - How long something would take if  It’s all you work on  You have no interruptions  You have all you need  Elapsed time is total time taken to finish the work  Think of how many productive hours a day you usually have.  Ideal time for a American footwall game is 60 minutes – Four 15 minutes quarters. The elapsed time is much longer and hard to accurately predict.  Ideal Days estimate is easy to estimate and explain but hard to convert into elapsed time.  Trainings, meetings, phone calls and task switching etc affect difference between ideal time and elapsed time. Ref: Mike Cohn’s “Agile Estimating and Planning”
  9. 9. Relative Estimation Small Medium Large Can you divide mangoes from this huge pile into three boxes based on size? Do you need to be told the exact dimension, length, width etc to identify different sizes? Giving measurement baselines will not help because:  It’s very difficult and time consuming to measure.  Given dimensions might not be accurate and result in all or most going to a single box.  Triangulation will help. Triangulation means comparing each sample with multiple other samples.  Relative estimation is slow and difficult in the beginning but once you have estimated few, it will be fast and easy.
  10. 10. Estimating in Story Points  Story Point is relative size / “bigness” of task  Depends on “how hard it is”  Depends on “how much there is”  Relative values are what is important  A login screen is 2; A search feature is 8  Smallest story point could be of 1 story point  Unit-less points  Don’t use a single gold standard – Triangulate  Triangulation means comparing the story with multiple other stories.  Each team defines them as they see fit. We can’t compare story estimates of two different teams.  Easier to estimate, harder to explain.  Basic math functions (addition, subtraction etc) still hold good. User Story As a user, I want to check my reservations Ref: Mike Cohn’s “Agile Estimating and Planning”
  11. 11. Comparing Approaches – Ideal Days  Ideal days can force companies to confront time wasting activities  Ideal days are easier to explain outside the team as the effort estimation in hours/days is widely known  The estimate will depend on who is doing the estimate  Ideal days are easier to estimate at first  For same amount of work, ideal days estimate will change as team gains more experience. Ref: Mike Cohn’s “Agile Estimating and Planning”
  12. 12. Comparing Approaches – Story Points  Story points help drive cross-functional behavior. Whole team irrespective of speciality has to provide a single estimate (NOT sum of individual estimates)  Story points are a pure measure of size  Story point estimates do not decay. As it’s relative, for same amount of work, estimate will not change with time.  Estimating in story points is typically faster  Most of the agile experts favor story point estimation.  Story point estimation is difficult for new agile teams so one mid-way approach could be:  Define “1 story point = 1 ideal day”  Gradually convert team to thinking in unit-less story points Ref: Mike Cohn’s “Agile Estimating and Planning”
  13. 13. Tips & Techniques for Estimation  Estimates are shared – estimation should be done collaboratively by team – by the people who would do the job.  Single estimate by cross functional team  Estimate by Analogy  “This story is like that story”.  Triangulate!  Top down estimate – Try to be more precise for work to be done in near future.  Disaggregation - Break a big story/epic into smaller stories or tasks  Use a good estimation scale Ref: Mike Cohn’s “Agile Estimating and Planning”
  14. 14. Agile Estimation - How Much Effort?  A little effort helps a lot  A lot of effort only helps a little more Accuracy Effort
  15. 15. Agile Estimation – Using the right scale  Can you decide whether given story is a one point story OR a two points story?  How about deciding whether given story is a 14 points story OR a 15 points story?  Use a non-linear scale. Two commonly used scales are:  Fibonacci Series – 1,2, 3, 5, 8, 13, 20, 40, 100…  Power of two – 1, 2, 4, 8, 16…  For work to be done in near future, stay within single order of magnitude i.e. range 1 – 10  Include 0 or ½ if required.  Zero helps in considering trivial efforts.  Remember 15x0 != 0. Multiple zero point stories can be combined to make 1-2 points stories. Ref: Mike Cohn’s “Agile Estimating and Planning”
  16. 16. Agile Estimation – Just in time Each of the priority items has a size estimate in story point or ideal days Very large item at the bottom may not have estimate or may have estimate in large units As items move up in the priority list of unfinished items, these are refined further for better estimate Accuracy 2 3 1 3 5 8 3 13 20 40 100 L XL
  17. 17. Planning Poker  Planning poker is a variation of Delphi method.  An iterative approach to estimating The key steps are: 1) Each estimator is given a deck of cards, each card has a valid estimate written on it (based on non-linear scale chosen) 2) Customer/Product owner reads a story and it’s discussed briefly 3) Each estimator selects a card that’s his or her estimate 4) Cards are turned over so all can see them 5) Discuss differences (especially outliers) 6) Re-estimate until estimates converge 7) Product owner or customer doesn’t estimate but is present to answer any queries around scope. Ref: Mike Cohn’s “Agile Estimating and Planning”
  18. 18. Planning Poker example Estimators Round 1 Round 2 Tara 3 5 Bala 8 5 Joju 2 5 Chris 5 8 Ref: www.PlanningPoker.com
  19. 19. Why does Planning Poker work?  Those who will do the work, estimate the work  Everyone’s opinion is heard – helps in buy-in and improve team collaboration  Estimators are required to explain reasoning  Combining of individual estimates through group discussion lead to better estimates  There are limited set of values so no wastage of time in meaningless arguments  Quick and Fun  In summary, it combines the best of following three most common techniques of estimation:  Expert Opinion  Analogy  Disaggregation Ref: Mike Cohn’s “Agile Estimating and Planning”
  20. 20. Velocity  Velocity is a measure of a team’s rate of progress.  Sum of story points assigned to each completed user story in the iteration.  Helps in determining how much can be done  Schedule = (Total number of story points / velocity)*Iteration length  Velocity corrects estimation errors. Size Velocity Duration 200 Points Velocity = 25 200/25 = 8 Iterations
  21. 21. Thank You 

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