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Software estimation is crap
The document critiques the reliability of software estimates, highlighting their tendency to be significantly inaccurate due to complexities in software development compared to manufacturing. It discusses psychological factors affecting estimation and the detrimental effects of estimates on project management, such as mismanaged expectations and focus misalignment. Recommendations include using relative sizing, emphasizing feasibility, and shifting away from traditional estimation methods in favor of more adaptive planning approaches.
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Software estimation is crap
- 1. Why are Software Estimatesa Load of $#&%? (YEAH, THAT’S AN INFLAMMATORY TITLE)
- 2. How many ofyou estimate?
- 3. How many ofyou have been wrong with estimates?
- 4.
- 5.
- 6. What do wedo about it?
- 7.
- 8. This isn’t aboutthat…
- 9.
- 10. Ian Garrison Agile Coach,Engineer, Life Long Learner ◦ MEng ECE ◦ SPC ◦ Agile Midwest Bear ◦ Former radio DJ and farmer Agile coach with ian@sketchdev.io
- 11. Ian Garrison Agile Coach,Engineer, Life Long Learner ◦ MEng ECE ◦ SPC ◦ Agile Midwest Bear ◦ Former radio DJ and farmer Agile coach with ian@sketchdev.io Guy who hates wasting time on things that don’t add value
- 12. What is anestimate? A PRIMER
- 15. 0 0.2 0.4 0.6 0.8 1 0 0.05 0.1 0.15 0.2 0.25 0.3 0 1 23 4 5 6 7 8 9 10
- 16. 0 0.2 0.4 0.6 0.8 1 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0 2 46 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100
- 18. — Central LimitTheorem The arithmetic mean (and sum) of a sufficiently large number of iterates of independent random variables, each with a well- defined expected value and well-defined variance, will be approximately normally distributed, regardless of the underlying distribution.
- 19.
- 20. Works great inmanufacturing! • Many units • Independent failures • Known, repeatable process • Complicated problems
- 21. Not so greatwell for software… • Few units • Lots of dependencies • Complex problems • Pesky humans! Works great in manufacturing! • Many units • Independent failures • Known, repeatable process • Complicated problems
- 22.
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- 27. Mode < Median< Mean
- 28. Mode < Median< Mean (Most common) (Middle) (Sum / Count)
- 29.
- 30.
- 31.
- 32.
- 33. You can’t takeless than zero time
- 34. You can takeinfinite time But you can take infinite time
- 37. Just add abuffer! Let’s get ready to… double all of our estimates!
- 38. Parkinson’s Law A.K.A. BUFFERSDON’T WORK!
- 39. “It is acommonplace observation that work expands so as to fill the time available for its completion.” — C. Northcote Parkinson
- 40.
- 41.
- 42. Why padding doesn’twork Padding is a mutually-agreed-upon delusion No respect for the time Decreases the sense of urgency Estimates are too short to begin with Student Syndrome
- 43. The Psychology of Estimation OR,WHY PEOPLE CAN’T PREDICT THE FUTURE
- 44. Canada Roger Buehler Psychology DepartmentWilfrid Laurier University Dale Griffin Department of Commerce University of British Columbia Michael Ross Department of Psychology University of Waterloo
- 45. Round 1: Predictingcompletion dates Who: A bunch of college students The question: When will you be done with your final paper for the class, with 50%, 75% and 99% confidence?
- 46. People underestimate Ask peoplewhen they will be done 13% finish by their 50% confidence time 19% finish by their 75% confidence time Only 45% finish by their 99% confidence time
- 47. That’s pretty bad,but college students procrastinate more, right?
- 48. Maybe we askedthe wrong questions…
- 49. Round 2: Settingthe right context Who: A different bunch of college students The question: Give me your “best guess” estimate, and then give me your “best case” estimate
- 50. Asking for arealistic “best guess” scenario
- 51. vs. asking foran ideal “best case” scenario
- 52.
- 54. Round 3: Arethey thinking about this? Who: A different different bunch of college students The question: Estimate how long it will take, but break it down into tasks
- 55. Detailed estimation When askedto break down work into more discrete pieces, people become more optimistic and less accurate in overall estimation.
- 56. “Nothing in lifeis as important as you think it is when you are thinking about it.” — Daniel Kahneman Reference-class forecasting Nobel Prize in Economics, 2002
- 57. Estimation is harmful (GETTO THE POINT ALREADY)
- 58.
- 59. …give you afalse sense of security…
- 60. …and distract you fromfocusing on the right things
- 62. What else canwe fit?
- 63. What should wedo next?
- 64. It’s easy togame the system by working on what is easiest, not what is most important
- 65. Goal Θ Relevance How much ofyour velocity is relevant?
- 66. How much isover-production?
- 67. Why do weestimate?
- 68. Why do weestimate? Decide whether to invest/undertake a project Coordinate release timing with Marketing/Customer Support/Sales Figure out if we need to hire more people Plan cross-team dependencies Generate a long-term roadmap based on resource bandwidth
- 70. Decide whether toinvest/undertake a project Coordinate release timing with Marketing/Customer Support/Sales Figure out if we need to hire more people Plan cross-team dependencies Generate a long-term roadmap based on resource bandwidth Why do we estimate? Fund products and value streams and revisit funding based on ROI Smaller cycles and improved transparency and coordination Staff to investment. Ramp-up times are looooooooooooooong Field cross-functional teams. New architectures to decouple dependencies Focus teams on single problems/products. Embrace change
- 71.
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- 73. Plan for failure FAILINGTO PLAN IS PLANNING TO FAIL…ERRRR WAIT…
- 74. Expect the best,plan for the worst, and prepare to be surprised. — Denis Waitley
- 75. “We don’t havea plan for this” — Rudy Giuliani
- 76.
- 77. (Yes, I justspent the last umpteen minutes telling you how harmful estimation is and now I’m telling you to estimate)
- 78. “With great powercomes great responsibility” — Uncle Ben and a whole lot of people before that
- 79. What estimates aregood for… Relative sizing (it’s bigger than a breadbox, smaller than a house) Is something feasible? Considering the problem and solution Guiding milestones
- 80. What estimates arebad for… Determining a ship date (for anything remotely complex) Capturing complex cost/benefit scenarios, like refactoring Managing scarce resources – budgets are better
- 81.
- 82. My Rules forEstimating IN A TOTALLY NON-EVIL WAY
- 83. Rule #1 Break thingsdown small
- 84. Rule #2 Use abstractunits for estimates
- 85. Rule #3 Don’t wastetime on close
- 86. Rule #4 Don’t trustan estimate
- 87. Rule #5 Estimating ≠Planning
- 91. No tool willmanage the project for you
- 94.
Editor's Notes
- #13 Let’s start with basic probability
- #14 Flip a fair coin
- #18 Reality is more complicated Behind each task is a range of times with a different chance for each one
- #21 Maxim: You can’t manage what you can’t measure
- #26 1:6 projects take > 200% over cost and 70% over schedule Hides real costs… Levi’s - $5M project led to $195M write off Healthcare.gov British supermarket chain declared bankruptcy over failed
- #36 Doesn’t matter so much when you are producing millions of toys Mean error rate works pretty well
- #37 Matters quite a bit when you have schedule dependencies across teams Size and direction of error causes cascading delays
- #40 1955 Economist article, that was originally discussing the inefficiency of bureaucracies
- #43 Managers know there is a buffer and fill it with unplanned tasks, because hey, it was extra time to begin with
- #45 Since the mid 90s, A group of professors in Canada have produced some interesting research into the psychology of estimation
- #54 When asked for a realistic scenario, most people envision everything going exactly as planned, with no unexpected delays or unforeseen catastrophes. The same vision as their “best case” – http://lesswrong.com/lq/jg/planning_fallacy
- #56 Even when they are confronted with visualizing the worst-case scenario.
- #57 Reference-class forecasting Daniel Kahneman: Thinking Fast and Slow
- #62 Encourages managing by packing boxes
- #75 Plans go wrong, and go wrong regularly
- #76 Generators for electricity – blackout Hospitals & Triage – disease outbreak Crowd control & policing – terrorist attack
- #81 Budgets are better for managing scarcity
- #84 Not to get better accuracy in your estimates, but to identify what not to build. YAGNI. Reclaim up some of your time. Get smaller as you get closer to building things.
- #85 Story points, T-shirt sizes, Jelly beans. People are better able to step back and consider complexity instead of calendar. Of course, once you bring velocity back into it…
- #86 If you’re deciding between 2 points or 3 points, it’s 3. Move along.
- #87 As an aggregate they kind of make sense in the short term. Beyond that, it’s the priorities that change, not the tasks. Manage your projects
- #88 As an aggregate they kind of make sense in the short term. Beyond that, it’s the priorities that change, not the tasks. Manage your projects
- #92 Actively work to remove the bias of your expectations
- #93 manage relentlessly, in real-time.
- #94 If you don’t actively manage scope and priorities, you will miss all deadlines.