2. 2-2 Estimating Size in Ideal Days

3. Outline Ideal vs. elapsed time Ideal time as an estimate of size
Comparison between story points and ideal days

4. Ideal vs. elapsed time How long is a soccer game?
Two 45-minute periods
1 hr 45 min – 2 hrs
Ideal time: time that something takes when stripped of all peripheral activities
Elapsed time: time that passes on a clock/calendar

5. Ideal time is easier to estimate
It’s easier and more accurate to predict ideal time than elapsed time
For elapsed time you need to consider external factors
Example: in a soccer game’s elapsed time we need to consider penalties, injuries, weather…

6. Ideal time in the software context
Ideal time: time it would take to completely finish a user story if
It’s all you worked on
You had no interruptions
All the resources you needed were available

7. Why ideal time ≠ elapsed time
Vacations
Meetings
Phone calls
Training
Interviewing
Debugging current releases
Task switching due to multitasking …

8. Example
Ideally
Monday has 8 work hours
Monday has:
3 hours of meetings
1 hour of
4 hours left for the project
But instead
Therefore, this developer will take two calendar days to complete one ideal day of work

9. Ideal time as an estimate of size
Instead of story points, we can estimate the size of a user story by estimating the ideal time it will take to finish it
Velocity will now be in units of _________
Example: How many weeks will it take to create an 80 ideal-day project if a team’s velocity is estimated at 8 ideal days per 2-week iteration?
20 weeks

10. Ideal time of the group not individuals
If two people work on a story for a full day = 2 ideal days
To stay simple and to keep the “we’re all in this together” mentality, avoid writing separate estimates for each team member
Example: not 4 programmer days + 2 tester days – just say 6 ideal days
Not worth the extra effort

11. Story points vs. Ideal days
Now, what’s a better unit for estimating size: story points or ideal days?

12. In favour of story points…
Story points help drive cross-functional behaviour
Story point estimates don’t decay
Story points are a pure measure of size
Estimating in story points is typically faster
My ideal days ≠ your ideal days

13. Story points help drive cross-functional behaviour
Story point estimates are based on discussions that result in one number representing all of the work for the whole team
In ideal days, members start to think about how long “their part” will take

14. Story point estimates don’t decay
An estimate in ideal days can change based on a team’s experience
Example:
Developer estimates a small application written in a new language as 5 ideal days
Same developer 1 month later estimates an equally small application as 1 ideal day, because she now has experience with the language
Problem: 2 applications of the same size with 2 different size estimates

15. Story points are a pure measure of size
Because it’s size, we can estimate story points by analogy only
Studies show we are better at relative estimating. We’re better at estimating “this is like that” than we are at the absolute size of things
No temptations to compare them to reality and pressure to make actual day = ideal day
Boss: “Why did you only complete 8 ideal days of work in a 10-day iteration?”

16. Estimating in story points is faster
When using ideal days, we tend to think about the details and tasks necessary to develop the story
Story point discussions are more focussed on high-level discussions

17. My ideal days ≠ your ideal days
One fast runner and one slow runner stand before a 1km race
They agree on the size (1km) of the race
Fast runner says it will take her 5-min; Slow runner says 8-min ?!
Same problem exists in ideal days. Usually resolved by:
Programming in pairs
Having teams of similar skill
Putting the estimate of the person likely to work on it 

18. In favour of ideal days…
Ideal days are easier to explain outside the team
Ideal days are easier to estimate at first

19. Ideal days are easier to explain outside the team
Ideal days have an intuitive feel which makes them easy to understand and explain
However, explaining story points is a good opportunity for introducing other important agile estimation concepts
Concepts such as cone of uncertainty, velocity, …

20. Ideal days are easier to estimate at first
Compared to ideal days, estimating in story points can be difficult and strange at first, especially with no baseline of previously estimated stories to compare with
However, this feeling quickly diminishes

21. Conclusion
Based on the advantages of story points, we will insha Allah be using them for the rest of our work in this course

22. Conclusion: Test your understanding
List three reasons why elapsed time does not equal ideal time.
It’s easier and more accurate to predict elapsed time than ideal time. T/F?
When estimating in ideal time, assume: (1)_______, (2)________, (3)__________
State two advantages in favour of story points.