User Stories Applied:

For Agile Software Development

–

Ch 8. Estimating User Stories

Chen Jing Fung @iii

2011/6/20

Ref: How to write, gather ideas,

http://fungsiong.blogspot.com/

Estimating user stories

• The reason:

– Every project (story) has it time limit!! => need

to understand how long will finish

• Basic idea about estimation

– Story points (basic unit in estimation)

• Each team has their nice feature of story points in

the elapsed time

– A ideal day > A ideal week

– Estimate as a team > a individual

• Don’t know who will join the stories

• The team involved in coming up with the estimates

No meetings, no email, no phone calls …

Force to

consider all

other possible

impacts

For a complexity story

Story points – estimation method (1)

• Estimating (vertical)

– Key: every story isn’t

same

– Talk with customers

– Set story points

• 20 * 1 point > 1* 20

points

• Share some reasons

– Triangulate the estimates

customer

developers

Before

ask

Ans. After

1st round:

5 3 1

2nd round: Moving close (converge)

4 4 3

40, 80 >

79, 80

To close

1 2 3 5 8 13

point range: ½ , 1, 2, 3, 5, 8, 13, 20, 40, 80

Compare with the others

Accuracy !!

point

uncertainty

Story points – estimation method (2) • Using Story Points

– After finished an iteration, the team can counts # of story points (= velocity)

• based on 1st iteration <= Good!!

• Accuracy isn’t important – Total: 300 points

– 1st iteration: done 50 points/week > predict: 30 points/week (what is velocity? 30 or 50)

– 3 conditions to keep velocity on 1st iteration

» Nothing unusual (no accident), using a consistent manner, 1st iteration must be independent

– The Central Limit Theorem: Σ #independent samples ~ normally distributed

• Pair program – No effect on story point estimates

– Relevance with velocity!! • Ex:

3 3 , Velocity

= 6 p/w

Velocity

= 4 p/w

Based on

ideal day Based on

Ideal pair

days

Summary

• Use story points, keep some facts in mind – Your team’s points ≠ my team’s

– Σ #story points ≠ Σ #individual stories points ≠ Σ #task story points

• Estimate stories in story points – Consider: complexity, effort or duration of a story

• Estimate points based on a team > individuals

• Triangulate an estimate by comparing it to other estimates

• Pair program just affect to the velocity – Not story points Ref: How to write, gather ideas,

http://fungsiong.blogspot.com/