The Team Estimation Game is the best technique we have found to get a scrum team up-and-running with useful estimates. It plays like a game, but it accomplishes valuable work: assigning story point estimates to user stories.
Teams using this technique are typically able to estimate 20 to 60 stories in an hour. The game was invented by our friend and colleague, Steve Bockman. Here is how one team plays the game:
Team Estimation Game Part I: The Big Line-up
Frank, the team’s scrum master, has cleared space on a long section of wall in the team room, and now the team assembles in front of it. Brad, the product owner, has brought a stack of 30 user stories from his product backlog, and the team is going to size them by playing the Team Estimation Game.
“Kira, why don’t you go first?” Brad says, passing her the stack of story cards. Frank, who is holding a roll of blue painter’s tape, peels off a small piece and hands it to her.
Kira starts the game by taking the top story from the deck, reading it aloud, and taping it to the middle of the wall. Then she hands the deck off to Kai, who goes next.
Kai picks the next story off the top of the deck and reads it to everyone. “I think this one is bigger than the one Kira just placed,” Kai says, affixing his story to the right of Kira’s story.
Mark goes next. The story he reads strikes him as a small one, so he places it just to the left of the others.
Now Jeff picks a story off the pile. “This one is pretty small, too.” He hesitates, then moves Mark’s small story further to the left to make room for his. “But not as small as the one Mark just placed.”
The team continues to take turns placing stories. On Kira’s third turn, she doesn’t take a new story off the pile. Instead, she repositions one that is already on the wall, moving it further to the right. “Trust, me,” she says, “the legacy code for this one is a mess, and we are going to have to make it all thread-safe for this story to work!”
Soon enough, all of the stories have been placed on the wall—but the team continues to take turns. Now, instead of placing new stories, they are fine-tuning the order by moving them one at a time, sometimes silently, sometimes with a few words of explanation.
“Pass,” Malay says when his next turn comes, indicating that he is satisfied with the order of the stories. Justus passes during this round as well. Kira and Mark each move one more story, but pass on the next round. Eventually there is a round where they all pass. Part one of the Team Estimation Game is over!
The team now has their stories ordered left to right, smallest to largest. The story they all agree will require the least amount of work is farthest to the left, and the one that they believe will require the most amount of work is farthest to the right. What is remarkable is that the whole team has now achieved consensus agreement on the correctness of this ordering!
For those who have been paying close attention, you may have noticed that this game has the potential for an infinite loop. Mark might place a story to right, but then Kira could move it back to the left. Mark, in his next turn could move it to the right again, and so on forever. While the infinite case is theoretically possible, we have never encountered it the hundreds of times we have played the game.
Team Estimation Game Part II: What’s Your Number?
In preparation for round two of the Team Estimation Game, Frank produces a deck of Fibonacci cards. Each card in this deck has one of the Fibonacci numbers on it, from one to 144.
Mick starts off. He goes up to the wall and points to the leftmost story, vamping a bit like Vanna White on Wheel of Fortune. “This, ladies and gentlemen, is about the smallest story we are likely to see.” He tapes the Fibonacci card labeled “1” above the story.
Justus goes next. He holds up the card labeled “2” and considers the wall of stories, searching for the point where the stories on the wall start to be about twice as much work as the story with the “1” over it. He chooses his spot, and places the “2” card above a story that lies four cards in from the left.
Play continues for several rounds, with each team member placing a Fibonacci card above the row of stories where they believe a size break occurs.
When her next turn comes, Kira hesitates, then points to two stories. “You know,” she says. “I think we may want to reverse the order of these two. I think this one is an eight, and the other one is a 13.” She uses her turn to switch the order of the two story cards and hands the deck to Mark.
Mark places the “21” card above a story. Malay is next. He shakes his head, then removes the “21” card Mark just placed. “I think this is actually a 34,” he says, naming the next-highest number in the Fibonacci sequence. He replaces the “21” card with the “34” card.
“He’s right,” says Jeff.
Jeff helps Malay move the story cards just enough to create a blank space between the last size 13 story and the first size 34 story—when the team placed the story cards in round one; they left ample space between them to allow for this, knowing that things can shift during part two.
Malay tapes the “21” card above the blank space in the row of stories, to indicate that there are no stories of that size.
When everyone has reached the point where they feel confident enough in the sizes to pass on their turn, the game is over.
Now the team tidies up, moving the story cards to form columns under the Fibonacci cards. All the stories between the “1” and the “2” are collected in a single column under the “1” card; these are the one-point stories. The next column consists of all the two-point stories, and so on. The team never did put any stories under the “21, ” so that column remains empty.
What we’ve described is the simplest form of the game. When you play it on your team, note that you don’t have to start with a “1” as your smallest story size. If a player thinks there may be future stories that will be significantly smaller than the smallest story that is currently on the wall, they may opt to start with the “2” or “3” above the first story instead of the one. This leaves room for future stories to be sized smaller than the smallest story in the current set. For example, by placing a “2” over the leftmost, smallest story card, a player signals their belief that the team may encounter future stories that are half as much work to implement.
We teach this game to the teams we work with, and many of them tell us that they have never before started a project with the whole team believing that the estimates were correct. This is the way to build a plan that everyone actually believes in!
Excerpted from The Elements of Scrum, by Chris Sims & Hillary Louise Johnson.
©2011 Chris Sims, Hillary Louise Johnson and Agile Learning Labs. All rights reserved.