Fibonacci Series = Accurate Agile Estimates?
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2018-06-20に共有
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The Fibonacci Series is in common use in the Agile world. In this video, we'll look at how it helps with RELATIVE estimates...
... and we'll try to answer the question: "Does the use of the Fibonacci Series lead to more ACCURATE estimates?"
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123. Fibonacci Series = Accurate Agile Estimates?
#DevelopmentThatPays
Estimating is hard ---- If you've been following along with this series on agile estimating you'll have got the message by now that estimating is hard. But some estimates are much easier then others. We've talked previously about estimates of absolute size versus estimates of relative size. "How heavy is this " is a hard question. "Which of these is heavier " is an easy question. Why is it an easy question Well, it's because there's a large difference you assume in the weight of these two. When I say difference is that the absolute difference or the relative difference Which of these two coins is heavier Which of these two bridges is heavier I hope that answers the question. It's not the absolute difference that's important, it's the relative difference. The Fibonacci Series ---- Hold on a second. Wasn't this supposed to be an episode on the Fibonacci Series I think it's time we rolled it in. Actually, let's build it from scratch. The first two numbers are zero and one. To get the third we add the first two together: Zero plus one is one. We carry on adding pairs of numbers: 1 + 1 = 2 1 + 2 = 3 2 + 3 = 5 and so on: 8 13 24 34 55 89 It's in the spaces --- What's interesting in this series is the gaps between the numbers. Not the absolute gaps: the relative gaps. 0, 1 - The relative gap between these two is, oh, that's infinite. Yeah. That ones a little bit large. Let's move on. 1, 1 - the relative gap is zero 1, 2 - The relative gap between these two is 100%. Okay. 2, 3 - 50%. 3,5 - 66.6666667% 5, 13 61 and a bit percent. 13, 21 almost 62%. 21, 34 - 61.8%. 34, 55 -61.8% After some craziness at the beginning of the series the relative gap between he member of the series settles down to around 61 and a bit percent. Let me see if I can demonstrate that to you a little more visually. Here are the first few. Zero, one, one, two, three, five, ah, yeah now we're up to space. I'm going to zoom out around about 60%. There's the eight. Zoom out another 60% there's the 13. Zoom out again, 21. Zoom out once more, 34. Zoom out again, 55. Zoom out one last time, 89. I hope you can see that although the bars are getting skinnier as we zoom further and further out the relative size between this one and this one stays pretty well constant. Fibonacci for estimating ---- The reason that this scale works so well for estimating is that it encourages us to stay in the realm of easy estimates. It encourages us to stay with relative estimates. To say in slightly different terms if we are estimating two things and their sizes, their relative sizes are not sufficiently different then we consider that they both have the same size, which brings us right back to the question that we started with today. "Does the Fibonacci Series lead to more accurate estimates " I think the answer has to be no. If anything what it does is protect us from attempting to make accurate estimates. It keeps us in a realm of making rough or broad estimates.
• Fibonacci Series = Accurate Agile Est...
コメント (21)
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Here's the link to the Agile Estimating Cheat Sheet: www.developmentthatpays.com/cheatsheets/agile-esti…
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I think you missed something about the accuracy of Fibonacci series in estimation. Yes, it prevents us to make absolute estimations, but it's more than that : it helps us to keep in mind that complexity is not linear. Let's take an example. If you have x=3, it's preaty easy to solve. Having 3x+2y=12 will take more effort to solve. 2x-7y*12z=-182 will be clearly harder. Adding variables will not add "x values of effort" to solve, it will be more a multiplication (x1,6 as you demonstrate) Going from 3 to 5 means it will take more effort than going from 2 to 3, rather than 3 to 4. The more complexity you have, the more effort it will take. That's why Fibonacci series is accurate in agile : it has a great psychological impact on us about the reallity of complexity
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great video! thanks for making it. one of the best and simple explanation of the fibonacci usage in estimates. had to subscribe. keep up the good stuff sir!
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Good conclusion, thanks for the video.
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I watched "Agile Estimating & Planning [2018] Fibonacci Series = Better Estimates?", and was disappointed . The title of the presentation said "better" estimates, but the entire presentation was about "accurate" estimates. "Accuracy" is not the only characteristic of a "Better" estimate. IMHO, ease for the developer to make a useful estimate is more important. Nonetheless, I set out to 'fix' my set of numbers to see what difference that made. It turned out that my original list of sizes was fine for me. If I want to make relative estimates, I pay attention to the relative sizes of the estimates, not the relative gaps between sizes as was assumed in the video. I have watched several of your other videos, and generally found them helpful. Thank you.
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Thank you! I showed this to my team and they began to understand the importance of relative estimates and how it ties to the Fibonacci sequence. Im curious, how do you figure out the relative increase percentage? My team took this relative gap to say, "as the percentage decreases, the effort of each point increases. What are your thoughts?
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Thank you! This was very helpful!
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I’ve read chest sheet and I’m wondering - if I get You right You’r advice about estimating process is to ask many people and to ask questions like how many km are to dublin instead of when we’ll get there- but what if I must put a deadline ? How to estimate it rationally? Do You have tips?
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Great explanation. Do you have a video on building fibonacci burndown charts.
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Yep and they're crap. Great vid, thanks for confirming what I already knew is a concise manner!
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thanks for explaining this.
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In my previous post, I tried to use '-' to emphasize. The crossout that resulted was an unintended consequence. Sorry.
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Nice explaining bro
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Nice explained...👍
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Your cheat sheet has an error in the sequence - 20 not 21 - was that deliberate?
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Nice
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Hey Gary, can’t find the cheat sheet 🙈
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estimste on what ? what is the units? time, length, weight, dollars, life expectancy…
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The. target audience for this video appears to be those who are charged with managing software development teams. Like most tutorials on Agile or it’s components. But what is missing in almost all instructions on Agile are helpful instructions for the Worker Bees who are working in an Agile environment. Like most technical workers, I have no interest in becoming a manager and much less interest in being a Scrum Master. In my 4 decades of technical work I’ve always been baffled as to why senior managers like to take high performing technical workers and force them to do all the clerical work that goes with directing small to middle sized teams. Regarding this discussion of why a Fibonacci sequence is a wonderful example of how flawed Agile is. Yes your explanation of what the series is and the reality that once away from the first few numbers, the incremental increase between adjacent numbers converges on a fixed percentage increase. That reality has nothing to do with Agile and has been known for a couple of millennia. But in that respect, it is similar to many uses of the cosine function where in science and technology, there is a frequent need for a function with a shape similar to a cosine function. Since the cosine function is easy to describe and calculate, it is an attractive choice even though there is frequently no magic in the choice of cosine vs another similar shaped function. Project Management is an important function in any organization larger than a dozen staff. The needs of PM can easily become wasteful when the organization is working on objectives so innovative that things are dominated by Unknowable Unknowns. Certainly the motivation of Agile enthusiasts is laudable in that they want to reduce the waste of continually revising detailed Project Plans. But, Agile’s fatal flaw in that the Project Management staff who oversee the daily ,weekly, monthly implementation of Agile are generally technically weak on how to technical products that have business value.
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I use my own personal estimates
