I read, reviewed and digested the excellent The Art of Estimation by Steve McConnell and presented back what I'd learned about software estimation to the team.

1. The Art of Software Estimation
john burns

2. A presentation I put together as
part of a digestion and book review
of the excellent Art Of Estimation
by Steve McConnell. Any mistakes
or inaccuracies are entirely my own
doing.

3. What is an
estimate?

4. The client needs RiskForce IV before
next month or the Death Star will
implode.
How long do you think it will take?
P.s. We should softcode the
architecture in case we need to
integrate with their Other System
running on Paula Bean’s VM.
Love,
The Boss x

5. An estimate is an
unbiased, analytical
process to predict the
duration or cost of a
project.

6. We need
RiskForce IV
ready to demo
at a conference
in February.

7. We will have something to demo
at the conference in February.

8. It’s a prediction.
It is NOT planning!

9. Estimation is not 100% accurate
All estimates are probabilities

10. Why bother
making estimates
at all?

11. Better estimation…

12. Better planning…

13. Lower costs…

14. Greater chance of project success!

15. How do we know
if our estimate
is good?*

16. Hi RiskWorks!
A good estimate
should be within
25% of actual results
75% of the time.
Steve McConnell

18. For each question, fill in the upper and lower bounds that,
in your opinion, give you a 90% chance of including the
correct value.
Low High
estimate estimate
1. Surface temperature of sun
2. Latitude of Shanghai
3. Area of Asian continent
4. The year of Alexanda the Great’s birth
5. Total value of U.S currency in circulation in 2004
6. Total volume of the Great Lakes
7. Worldwide box office receipts for the movie Titanic
8. Total length of the coastline of the Pacific Ocean
9. Number of book titles published in the U.S. since 1776
10. Heaviest blue whale ever recorded

19. Answers
1. Surface temperature of sun 10,000°F /
6,000°C
2. Latitude of Shanghai 31 degrees North
3. Area of Asian continent 17,139,000 square miles
4. The year of Alexanda the Great’s birth 356 BC
5. Total value of U.S currency in circulation in 2004 $719.9 billion
6. Total volume of the Great Lakes 2.3 x 10^16 litres
7. Worldwide box office receipts for the movie Titanic $1.835 billion
8. Total length of the coastline of the Pacific Ocean 84,300 miles
9. Number of book titles published in the U.S. since 1776 22 million
10. Heaviest blue whale ever recorded 170 metric tons

20. How did you do?

21. Where did the
pressure to
narrow your
ranges come
from?

22. They came from within

23. Narrow ranges != greater accuracy;
Make your ranges
as wide as they
need to be

24. over
estimate?
under

25. Parkinson’s Law
Work expands to
fill time

26. Goldratt’s student
syndrome

27. Underestimating will
make them fearful,
increasing their rate
of work. The empire
will soon be mine.

28. Underestimating leads to project
plan destruction

29. More bugs

30. Bad team health
Bad team health
Image: sick

31. More time in status meetings
to discusstime spent in status meetings at the end of the project
More
slippage

32. Control the effects of
overestimation using
project planning and
status visibility
Not by buffering
your estimates

33. What’s the source
of uncertainty in our
estimates?

34. Cone of uncertainty

35. Cloud of uncertainty

36. The cone doesn’t
narrow
itself
You have to force it
to narrow by
reducing variability

37. Unstable requirements
are the worst offender

38. Project chaos leads to uncertainty in estimates

39. Remember to include:
Testing
Support of old projects
Version control
Building the installer
More meetings…

40. Optimism
is
bad

41. How do we become
better estimators?

42. Don’t give off the cuff estimates

43. Precision is not
accuracy
The project will not take
233.725 hours

44. Find something
meaningful to
count and keep
a record of it

45. Use expert judgement
only as a last resort

46. What about when you’re agile?

47. Measure story points
per sprint

48. Use t-shirt sizing
at the start of
the project
S, M, L

49. We can easily identify early on
anything not worth pursuing
T-Shirt sizing chart
Feature Business value Development cost
Feature A Large Small
Feature B Small Large
Feature C Medium Large
Feature D Medium Medium
…
Feature Z Small Small

50. We can be better at expert judgement

51. Make tasks more
granular
2 days max per task

52. Use ranges not single points
with best case and worst case
estimates
Feature Best Case Worst Case
Feature A 1.25 2.0
Feature B 1.5 2.5
Feature C 2.0 3.0
Feature D 0.75 2.0
Feature E 0.5 1.25
Total 6.0 10.75

53. Use the PERT formula to get the effort
in the Expected Case
Expected case =
[Best Case + 4(MostLikelyCase) +
WorstCase] / 6

54. Always compare your estimates
to your actuals or you’ll never be
a better estimator

55. Questions?