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Photo by gordon (TD8316) -Creative Commons Attribution-NonCommercial-ShareAlike License https://www.flickr.com/photos/2293...
Prediction is very hard, especially if it‘s about the future 
Nils Bohr
Exercise 1 –Expert estimation 
Write down your estimates for the following facts: 
1.Length of German border (in km) 
2.Am...
Why do we estimate?
●Prepare project bid 
●Plan time, resources, … 
●Foster discussion 
●Determine economic feasability 
●Someone told us so 
...
What do we estimate?
●Time 
●Effort 
●Complexity
How do we estimate?
Expert estimation 
●Ask someone who should know
Formal model 
•COCOMO 2, Function Points, IFPUG FPA, LOC, COSMIC Full Function Point (FFP) …
What could go wrong?
Insufficient data
Negotiation 
●Now cut that in half and we have a deal
Estimates become targets 
●But you’ve said it will take only so long!
Work expands so as to fill the time available for its completion. 
●Parkinson‘s Law
This is why buffers (or the Project Managers‘ multiplier) don‘t work.
Cycle of Mistrust 
Deliver the wrong thing, or late 
Trust breaks down 
Commitments of 
scope and time 
Focus on schedule ...
Good Practise
Clarify objectives 
•For which purpose? 
•What are the risks and mitigation strategies? 
•Awareness of the nature of estim...
Provide ranges not a single value 
Likely effort from … to …. 
Helps to communicate that an estimate is not a guarantee
Use indirection, avoid direct time estimates 
•Abstract units such as Story Points, Ideal Days or T-Shirt sizes help to co...
Explicitly state assumptions 
Provide a disclaimer: 
•Which assumptions 
•Use approach and data 
•Risks and possible impac...
Review and update your estimates 
•Use what you have learned 
•Do not hide unwelcome news 
•Burnt hours are a bad progress...
The evil of Fixed Price Contracts 
Knowing it will take longer does not help, because everything is fixed (unless people r...
Even better practise
•FOCUS ON VALUE 
•DELIVER SMALL SLICES 
•DELIVER EARLY & FREQUENTLY 
•CUSTOMER COLLABORATION 
© Copyright Neil Killick, It...
EMPIRICISM 
•Use actual results to predict progress
Useful Methods
Group Estimation 
Don‘t rely on a single opinion 
Methods: 
•Wideband Delphi 
•Planning Poker 
•Affinity Mapping
Analogy Method 
•Compare project to previous experience 
•Use checklist to compare and classify on different dimensions 
•...
Affinity Estimation 
•Silently order items relative to each other 
•Build clusters 
•Apply appropriate scale
Now it‘s your turn!
Exercise 2 –Affinity Estimation 
1.Take first item and place it in the center 
2.Take turns and position subsequent item r...
Exercise 2 –Affinity estimation 
Write down your estimates for the following facts: 
1.Length of German border (in km) 
2....
Exercise 2 –Solution 
Find the solution at http://yourprojectzone.com/2014/03/30/ uebung-team-estimation-game/
Thank you! 
Twitter: #PRubarth
Guesstimate - Some Thoughts on Estimation in Software Development
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Guesstimate - Some Thoughts on Estimation in Software Development

Common problems with estimation in Software Development and some ideas to overcome them.

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Guesstimate - Some Thoughts on Estimation in Software Development

  1. 1. Photo by gordon (TD8316) -Creative Commons Attribution-NonCommercial-ShareAlike License https://www.flickr.com/photos/22934398@N05 Created with Haiku Deck Guesstimate Peter Rubarth, 2014
  2. 2. Prediction is very hard, especially if it‘s about the future Nils Bohr
  3. 3. Exercise 1 –Expert estimation Write down your estimates for the following facts: 1.Length of German border (in km) 2.Amount of water in Bodensee lake (in l) 3.Dollars (as notes) in circulations within the USA in 2004 (in $) 4.Birth year of Alexander the Great (year) 5.World wide revenue with movie “Titanic” (in $) 6.Latitude of Shanghai (in degrees) 7.Temperature on the surface of the sun (in °C) 8.Number of bacteria in human intestines 9.Number of works of Ludwig van Beethoven 10.Expanse of Asia (in km^2) 11.Number of stars in Milky Way 12.Number newly published books in Germany 2004-2007 13.Area covered by Hamburger Hafencity including water area (in ha) Thankyou@projectzone-http://yourprojectzone.com/2014/03/30/uebung-team-estimation-game
  4. 4. Why do we estimate?
  5. 5. ●Prepare project bid ●Plan time, resources, … ●Foster discussion ●Determine economic feasability ●Someone told us so ●…
  6. 6. What do we estimate?
  7. 7. ●Time ●Effort ●Complexity
  8. 8. How do we estimate?
  9. 9. Expert estimation ●Ask someone who should know
  10. 10. Formal model •COCOMO 2, Function Points, IFPUG FPA, LOC, COSMIC Full Function Point (FFP) …
  11. 11. What could go wrong?
  12. 12. Insufficient data
  13. 13. Negotiation ●Now cut that in half and we have a deal
  14. 14. Estimates become targets ●But you’ve said it will take only so long!
  15. 15. Work expands so as to fill the time available for its completion. ●Parkinson‘s Law
  16. 16. This is why buffers (or the Project Managers‘ multiplier) don‘t work.
  17. 17. Cycle of Mistrust Deliver the wrong thing, or late Trust breaks down Commitments of scope and time Focus on schedule © Copyright Neil Killick, Iterative, 2013
  18. 18. Good Practise
  19. 19. Clarify objectives •For which purpose? •What are the risks and mitigation strategies? •Awareness of the nature of estimations?
  20. 20. Provide ranges not a single value Likely effort from … to …. Helps to communicate that an estimate is not a guarantee
  21. 21. Use indirection, avoid direct time estimates •Abstract units such as Story Points, Ideal Days or T-Shirt sizes help to communicate uncertainty •Support empiric forecasting
  22. 22. Explicitly state assumptions Provide a disclaimer: •Which assumptions •Use approach and data •Risks and possible impact At least you have told `em
  23. 23. Review and update your estimates •Use what you have learned •Do not hide unwelcome news •Burnt hours are a bad progress indicator
  24. 24. The evil of Fixed Price Contracts Knowing it will take longer does not help, because everything is fixed (unless people really idled before) Strong incentive to cut corners and damage quality
  25. 25. Even better practise
  26. 26. •FOCUS ON VALUE •DELIVER SMALL SLICES •DELIVER EARLY & FREQUENTLY •CUSTOMER COLLABORATION © Copyright Neil Killick, Iterative, 2013
  27. 27. EMPIRICISM •Use actual results to predict progress
  28. 28. Useful Methods
  29. 29. Group Estimation Don‘t rely on a single opinion Methods: •Wideband Delphi •Planning Poker •Affinity Mapping
  30. 30. Analogy Method •Compare project to previous experience •Use checklist to compare and classify on different dimensions •Only useful if sufficient similarity
  31. 31. Affinity Estimation •Silently order items relative to each other •Build clusters •Apply appropriate scale
  32. 32. Now it‘s your turn!
  33. 33. Exercise 2 –Affinity Estimation 1.Take first item and place it in the center 2.Take turns and position subsequent item relative to existing items 3.Reorder if you disagree 4.Do not discuss!
  34. 34. Exercise 2 –Affinity estimation Write down your estimates for the following facts: 1.Length of German border (in km) 2.Amount of water in Bodensee lake (in l) 3.Dollars (as notes) in circulations within the USA in 2004 (in $) 4.Birth year of Alexander the Great (year) 5.World wide revenue with movie “Titanic” (in $) 6.Latitude of Shanghai (in degrees) 7.Temperature on the surface of the sun (in °C) 8.Number of bacteria in human intestines 9.Number of works of Ludwig van Beethoven 10.Expanse of Asia (in km^2) 11.Number of stars in Milky Way 12.Number newly published books in Germany 2004-2007 13.Area covered by Hamburger Hafencity including water area (in ha) Thankyou@projectzone-http://yourprojectzone.com/2014/03/30/uebung-team-estimation-game
  35. 35. Exercise 2 –Solution Find the solution at http://yourprojectzone.com/2014/03/30/ uebung-team-estimation-game/
  36. 36. Thank you! Twitter: #PRubarth

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