What do Planning Poker numbers represent? [closed]

Question

The numbers used to vote when planning are 0, 0.5, 1, 2, 3, 5, 8, 13, 20, 40, 100. Is there a meaning when those numbers are chosen? Why don't we just choose 1,2,3,4.. for the sake of simpliness?

Janellejanene

Does 40j mean "very imaginary" (sorry, couldn't resist) – Annoy

Someone edited out the "40j" in the original, rendering my joke meaningless – Annoy

I'm voting to close this question as off-topic because it is about managing programmers. This is not a code question. – Lenwood

Answer 1

The point is that as the estimates get bigger, they become less likely to be accurate anyway. There's no point in debating the merits of 34 vs 35 - at that point you're likely to be miles out anyway. This way just makes it easier: does this feel more like a 20-point task or a 40-point task? Not having the numbers between 21 and 39 forces you to make look at it in this "bigger" way. It should also be a hint that you should break the task down further before you come close to doing it.

Sikora

Good summary. I'll also say that you may find you want to limit the upper end of the scale. Some teams will do something like: 1, 2, 3, 5, 8, 13, + -- Where "+" means "too big". That's an indication the story should be split into smaller bits, which usually reduces risk. – Grenier

@James Cooper: Even better is to do something like 1, 2, 3, + -- where "+" means "too big". And then you don't have to worry about Fibonacci. ;-) – Interjacent

I love your idea @JamesCooper – Janellejanene

Answer 2

All the details are explained here: http://en.wikipedia.org/wiki/Planning_poker

The sequence you give has been introduced by Mike Cohn in his book "Agile Estimating & Planning" (therefore the sequence is copyrighted, you need to obtain the permission to use it or you can also buy decks from his online shop).

The original planning poker sequence is a bit different and described he by his original inventor (James Grenning) : http://renaissancesoftware.net/papers/14-papers/44-planing-poker.html

Hitch

Answer 3

This sequence allows you to compare backlog items to eachother. So it is imposible to say that some item is exactly two times bigger than other. Using this sequence you will always decide if it is more than two times bigger or less than two times.

For example: First Item is estimated as 3SP Now you are estimationg Second Item and someone said that it is two times "bigger" than First Item. Development tasks can't be exactly that same or exactle few times bigger or smaller. So you need to decide if it is bigger less than two times or more (it could be 5SP or 8SP).

If you have many estimated items in your backlog you can use this numbers for some stats. This stats works because Law of large numbers. http://en.wikipedia.org/wiki/Law_of_large_numbers

Using this sequence you are putting some uncertainty into that numbers so probability that this stats will work for you become higher.

Other simple answer for your question is: Mike Cohn chose this nubers after many experiments because they seams to work best in long period of time for various teams

All what I've wrote before is theory which has been created after experiments.

Fusilier

Answer 4

I've never seen that sequence used, the Fibonacci series (1 2 3 5 8 13 21 34) is more common. The idea is to avoid tricking yourself into thinking there is precision when there isn't.

Fantasize

The Online Encyclopedia of Integer Sequences turns up nothing! research.att.com/~njas/sequences/… – Kell

It's fibonacci to a point, with some roudning at higher numbers. I've seen it on a few sets of printed scrum cards before. Having a zero is useful, but 0.5 seems daft to me. – Devotee

@Dan No, it isn't. With time, you might find a smaller story than the smallest stories of the first sprints. This is where 0.5 comes in. – Gypsophila

Answer 5

Numbers on planning poker represent complexity of a task. You should not consider that a story with 8 as value is the double size in effort or time of a size 4 story for example. You could use as many different representations for these numbers as you want (like t-shirt sizes). You just need to have an idea that one value is more complex than another and there is another value that is even more bigger than it. The Planning Poker application attempt to illustrate this complexity with drawings related with number in order to help on this idea.

Misestimate

This answer ignores what you're generally trying to do with your estimates. You generally want to choose how many stories will fit into your sprint based on the estimates, in which case you absolutely do want an 8 to take (approximately) twice as long as a 4. Ditto for calculating a team's velocity and doing release planning. – Nahshon