A presentation on the practice of software estimation based on the book Software Estimation: Demystifying the Black Art.

1. The Practice of
Software Estimation
© 2008 by Phymata Solutions Inc. (Everett Toews)
This presentation may not be modified in any way.
Permission to use this presentation is granted to
eWorld ES Inc. provided this copyright notice is included.

2. Presentation Roadmap
©  Overview
2008 by Phymata
Solutions Inc.
 Techniques
(Everett Toews)
This presentation may
 Presentation
not be modified in
 Wrap up
any way.
Permission to use this
 Questions
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

3. Why Talk About Software
Estimation?
©  My Motivation
2008 by Phymata
Solutions Inc.
 Advancing the Art and Science of
(Everett Toews)
Software Development
This presentation may
not be modified in
 Making a living
any way.
Permission to use this
 My Experience
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

4. Current State of Software
Estimation
©  Most companies looking to avoid
2008 by Phymata
Solutions Inc.
estimates that are incorrect by 100% or
(Everett Toews)
more
This presentation may
not be modified in
 Goal – A good estimation approach that
any way.
provides estimates that are within 25% of
Permission to use this
the actual results %75 of the time
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

5. Estimates, Targets and
Commitments
©  Estimate (layman’s definition) – A prediction of
2008 by Phymata
how long a project will take or how much it will
Solutions Inc.
cost.
(Everett Toews)
This presentation may
 Target – A statement of a desirable business
not be modified in
objective.
any way.
Permission to use this – A promise to deliver defined
 Commitment
functionality at a specific level of quality on a
presentation is
certain date.
granted to
eWorld ES Inc. the target become the estimate
 Don’t let
provided this
copyright notice is
included.

6. What is a Good Estimate?
 Single point estimates are meaningless
© 2008 by Phymata
Solutions Inc.
(Everett Toews)
This presentation may
not be modified in
any way.
Permission to use this
presentation is
granted to
eWorld ES Inc.
provided this
 All estimates should include a probability
copyright notice is
included.

7. What is a Good Estimate?
©  Making a commitment
2008 by Phymata
Solutions Inc.
 Ability to support a project’s success
(Everett Toews)
This presentationproject targets
 Realistic may
not be modified in
 Estimate – A good estimate is an estimate that
any way.
Permission to usea clear enough view of the project
provides this
presentation is allow the project leadership to make
reality to
granted to decisions about how to control the project
good
eWorld ES Inc. targets.
to hit its
provided this
copyright notice is
included.

8. How Good an Estimator Are You?
1. Surface temperature of the Sun
© 2. Latitude of Shanghai
2008 by Phymata
Solutions Inc.of the Asian continent
3. Area
(Everett Toews) of Alexander the Great’s birth
4. The year
This presentation may US currency in circulation in 2004
5. Total value of
not be modified in
6. Total volume of the Great Lakes
any way.
7. Worldwide box office receipts for Titanic
Permission to use this
8. Total length of the coastline of the Pacific Ocean
presentation is
grantedNumber of book titles published in the US since 1776
9.
to
eWorldHeaviest blue whale ever recorded
10. ES Inc.
provided this
copyright notice is Quiz © 2006 Steve McConnell
included.
All Rights Reserved. Permission to copy this quiz is granted
provided that this copyright notice is included.

9. How Good an Estimator Are You?
1. 10,0000F / 6,0000C
© 2. 31 Phymata North
2008 by Degrees
17,139,000 miles2 / 44,390,000 km2
Solutions Inc.
3.
(Everett Toews)
4. 356 BC
This presentation may
5. $719.9 billion
not be modified15in
6. 6 x 10 gallons / 2.3 x 1016 liters
any way.
Permission to usebillion
7. $1.835 this
presentation is miles / 135,663 kms
8. 84,300
granted22 million
9. to
eWorld380,000 pounds / 190 tons / 170,000 kgs / 170
10.
ES Inc.
provided this tons
metric
copyright notice is Quiz © 2006 Steve McConnell
included.
All Rights Reserved. Permission to copy this quiz is granted
provided that this copyright notice is included.

10. 90% Confident
©  90% confident closer to 30% confident
2008 by Phymata
Solutions Inc.
(Everett Toews) ranges are more accurate?
 Narrow
This presentation may
 Pressure to provide narrow ranges is self
not be modified in
induced
any way.
Permission to use this
 Estimating unknown quantities
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

11. Overestimate or Underestimate
©  Arguments against overestimation
2008 by Phymata
Solutions Inc.
 Arguments again underestimation
(Everett Toews)
This presentation may
 Penalty for overestimation
not be modified in
 Penalty for underestimation
any way.
Permission to use this
presentationbest projects come from the most
 The
is
accurate estimates
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

12. Benefits of Accurate Estimates
©  Improved status visibility
2008 by Phymata
Solutions Inc.
 Higher quality
(Everett Toews)
 Better coordination with other departments
This presentation may
not be modified in
 Better budgeting
any way.
 Increased credibility
Permission to use this
presentation risk info
 Early is
granted to
 Predictability
eWorld ES Inc.
provided this
copyright notice is
included.

13. The Cone of Uncertainty
© 2008 by Phymata
Solutions Inc.
(Everett Toews)
This presentation may
not be modified in
any way.
Permission to use this
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

14. Where Does Estimation
Error Come From?
 Chaotic development process
©2008 by Phymata
Solutions Inc. requirements
Unstable
(Everett Toews) activities
 Omitted
 Unfounded optimism
This presentation may
not be modified in & bias
 Subjectivity
 Off-the-cuff estimates
any way.
Permission to use this
 Unwarranted precision
presentation is
 Unfamiliar business/technology area
granted to
 Simplification of the estimate
eWorld ES Inc.
 …
provided this
copyright notice is
included.

15. Estimate Influences
©  Size
2008 by Phymata
Solutions Inc.
 Diseconomies of scale
(Everett Toews)
This presentation may
not be modified in
any way.
Permission to use this
presentation is software being developed
 Kind of
granted to
 Personnel factors
eWorld ES Inc.
 Programming language
provided this
copyright notice is
included.

16. Estimate Influences
© 1. Product complexity
2008 by Phymata
Solutions Inc.
2. Requirements analyst capability
(Everett Toews)
This presentation may
3. Programmer capability
not be modified in
4. Time constraints
any way.
Permission to use this
5. Personnel continuity
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

17. Considerations in Choosing
Estimation Techniques
©  What’s being estimated?
2008 by Phymata
Solutions Inc.
(Everett Toews) size
 Project
This presentation may
 Development methodology
not be modified in
 Development stage
any way.
Permission to use this
 Accuracy possible
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

18. Count, Compute, Judge
Count Com put e
©What by Phymata
2008 Size, Features Size, Effort, Schedule, Features
Solutions Inc.M L
Size S SM L
St age Early-Late
(Everett Toews) Early-Middle
St yle Iter. & Seq.
This presentation may Iter. & Seq.
Accuracy High High
not be modified in
any way.
Permission to if possible
 Count use this
presentation is when you can’t count
 Compute
granted to
eWorld ES judgment alone as a last resort
 Use
Inc.
provided this
copyright notice is
included.

19. What to Count
©  Something that is highly correlated
2008 by Phymata
Solutions Inc.
 Something available sooner than later
(Everett Toews)
This presentation may
 Something that will produce a statistically
not be modified in
meaningful average
any way.
Permission to use this
 Understand what you are counting
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

20. Calibration and Historical Data
Calibrat e w it h Calibrat ion w it h Calibrat ion w it h
© 2008 byI ndust ry Average Dat a Organizat ional Dat a
Phymata Proj ect Specif ic Dat a
Solutions Inc. Effort, Schedule,
Size, Size, Effort, Schedule, Size, Effort, Schedule,
What Features Features Features
(Everett Toews)
Size SM L SM L SM L
This presentation may
St age Early-Middle Early-Middle Middle-Late
not yle modifiedSeq.
St be Iter. & in Iter. & Seq. Iter. & Seq.
Accuracy Low-Medium Medium-High High
any way.
 Industry data
Permission to use this
presentation is
 Organizational (Historical) data
granted to
eWorld ES Inc.data
 Project
provided this
copyright notice is
included.

21. Historical Data
©  Accounts for organizational influences
2008 by Phymata
Solutions Inc.
(Everett Toews)subjectivity, unfounded optimism
 Avoids
and politics
This presentation may
not be modified in
 Data to collect
any way.
Permission to use this Time and Defects
 Size, Effort,
presentation is
granted to to calibrate
 How
eWorld ES Inc.
provided this
copyright notice is
included.

22. Individual Expert Judgment
Use of St ruct ured Use of Est imat ion Est imat ing Task Comparing Task
© 2008Process
by Phymata Checklist Ef f ort in Ranges Est imat es t o Act uals
Effort, Schedule, Effort, Schedule, Size, Effort, Schedule, Size, Effort, Schedule,
Solutions Inc.
What Features Features Features Features
(Everett M L
Size S Toews) SM L SM L SM L
St age Early-Late
This presentation may Early-Late Early-Late Middle-Late
St yle Iter. & Seq. Iter. & Seq. Iter. & Seq. Iter. & Seq.
not be modified in
Accuracy High High High N/ A
any way.
Permission to usewhat?
 Expert in this
presentation is
 Structured expert judgment
granted to
 Granularity
eWorld ES Inc.
 Checklist
provided this
copyright notice is
included.

23. Use of Ranges
©  Single point estimates are bad
2008 by Phymata
Solutions Inc.
 Best case/Worst case
(Everett Toews)
This presentation may
 Optimistic worst cases
not be modified in
 Expected Case = [BestCase + (3 x
any way.
MostLikelyCase) + (2 x WorstCase)] / 6
Permission to use this
presentation is
 Task | Best | Most Likely | Worst | Expected
granted to
 Risk
eWorld ES Inc.
provided this
copyright notice is
included.

24. Compare Estimates to Actuals
©  Magnitude of Relative Error =
2008 by Phymata
Solutions Inc.
(ActualResult - EstimatedResult) /
(Everett Toews)
ActualResult
This presentation may
not be modified in
 Comparison
any way.
 Feedback
Permission to use this
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

25. Decomposition and Recomposition
Decom posit ion by Com put ing Best and
© 2008 byDecom posit ion by
Phymata Work Breakdow n Worst Cases f rom
Feat ure or Task
St ruct ure ( WBS) St andard Deviat ion
Solutions Inc. Effort, Features
What Size, Effort Effort, Schedule
(Everett Toews)
Size SM L ML SM L
St age Early-Late
This presentation may Early-Middle Early-Late
not yle modified Seq.
St
be Iter. &
in Iter. & Seq. Iter. & Seq.
Accuracy Medium-High Medium Medium
any way.
 Decomposition
Permission to use this
presentation is of Large Numbers
 The Law
granted to
 Decomposition via WBS
eWorld ES Inc.
provided this the Best Case and Worst Case
 Adding
copyright notice is
included.

26. Estimation by Analogy
Est imat ion by Analogy
©What by Phymata Schedule, Features
2008 Size, Effort,
Solutions Inc.M L
Size S
St age Early-Late
(Everett Toews)
St yle Iter. & Seq.
This presentation may
Accuracy Medium
not be modified in
any way.
 Simple process
Permission to use this
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

27. Estimation by Analogy
© 1. Similar previous project
2008 by Phymata
Solutions Inc.
2. Compare
(Everett Toews)
This presentation may
not be modifiedup the estimate
3. Build
in
4. Create an effort estimate
any way.
Permission to use this
5. Consistent assumptions
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

28. Proxy-Based Estimates
St andard
© 2008FuzzyPhymata
by Logic Component s
St ory Point s T-Shirt Sizing
Size, Effort, Schedule, Effort, Cost, Schedule,
Solutions Inc.
What Size, Features Size, Effort Features Features
(Everett Toews)
Size ML SM L SM L ML
This presentation may Early-Middle
St age Early Early-Middle Early
St yle Seq. Iter. & Seq. Iter. & Seq. Seq.
not be modified in
Accuracy Medium Medium Medium-High N/ A
any way.
Permission to use this
presentation is proxy
 Identify
granted to
eWorld ES Inc. or count the proxy
 Estimate
provided this
copyright notice is
included.

29. Proxy-Based Estimates
©  Fuzzy Logic
2008 by Phymata
Solutions Inc.
(Everett Toews) Components
 Standard
This presentation may
 Story Points
not be modified in
 T-Shirt Sizing
any way.
Permission to use this
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

30. Expert Judgment in Groups
Group Review s Wideband Delphi
©What by Phymata Schedule, Features Size, Effort, Schedule, Features
2008 Size, Effort,
Solutions Inc. L
Size M ML
St age Early-Middle
(Everett Toews) Early
St yle Iter. & Seq.
This presentation may Seq.
Accuracy Medium Medium
not be modified in
any way.
Permission to Reviews
 Group use this
presentation is
 Wideband Delphi
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

31. Software Estimation Tools
Sof t w are Est im at ion Tools
©What by Phymata Schedule, Features
2008 Size, Effort,
Solutions Inc.L
Size M
St age Early-Middle
(Everett Toews)
St yle Iter. & Seq.
This presentation may
Accuracy High
not be modified in
any way.
Permission to useproject outcomes
 Simulate this
presentation is
 Probability analysis
granted to
eWorld ES Inc. for diseconomies of scale
 Account
provided this for creeping requirements
 Account
copyright notice is
included.

32. Software Estimation Tools
©  Estimation of less common software
2008 by Phymata
Solutions Inc.
issues
(Everett Toews)
 Planning options and tool integration
This presentation may
not be modified in
 What-if analysis
any way.
Permission to use this
 Referee unrealistic project expectations
presentation is
 Objective authority
granted to
eWorld ES Inc.
provided this checking manual estimates
 Sanity
copyright notice is large projects
 Estimating
included.

33. Software Estimation Tools
©  Data needed to calibrate tools
2008 by Phymata
Solutions Inc.
(Everett Effort in staff months

Toews)
 Schedule
This presentation may
not be modified in
any way.Size in LOC

 Available tools
Permission to use this
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

34. Use of Multiple Approaches
©  No single estimation technique is perfect
2008 by Phymata
Solutions Inc.
 Convergence is good, spread is bad
(Everett Toews)
This presentation may
 Misconceptions
not be modified in
 Different results
any way.
Permission to use this
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

35. Flow of Software Estimates on a
Well-Estimated Project
Changing t o More Accurat e Est im at e Ref inem ent Based
© 2008 by Phymata Lat er in t he
Met hods on Proj ect -Specif ic Dat a
Solutions Inc. Effort, Schedule, Features
What Size, Size, Effort, Schedule, Features
Size ML
(Everett Toews) SM L
Thisage
St presentation may
Early-Late Early-Late
St yle Seq. Seq.
not be modified in
Accuracy High High
any way.
 Poorly estimated projects
Permission to use this
presentationestimated projects
 Well is
granted to
 Size > Effort > Schedule | Cost | Features
eWorld ES Inc.
provided this
copyright notice is
included.

36. Well Estimated Projects
©  Reestimate
2008 by Phymata
Solutions Inc.
 Refinement
(Everett Toews)
This presentation may
 Make up the time
not be modified in
any way.Add the time

Permission to use this whole schedule by the magnitude
 Multiply the
presentation is
of the slip
granted to
 Presenting reestimation
eWorld ES Inc.
provided this
copyright notice is
included.

37. Standardized Estimation
Procedures
©  Protects against
2008 by Phymata
Solutions Inc.
(Everett Off the cuff estimates

Toews)
 Guessing
This presentation may
not be modified in
any way.Changing the estimate because a stakeholder

Permission to use this it
doesn’t like
 Encourage consistency
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

38. Elements of Standardized
Procedures
 Emphasizes counting and computing
©2008 by Phymata
Solutions Inc. estimation approaches
Multiple
 Reestimation
(Everett Toews)
 Approach changes over the course of a project
This presentation may
 Clear description of estimate’s inaccuracy
not be modified in
 When it can be used as a basis for internal and
any way.
external commitments
Permission to use this
presentation is estimation data for later review
 Archiving
granted to
 Deviations should be documented and rare
eWorld ES Inc.
provided this when estimation occurs in SDLC
 Define
copyright notice is
included.

39. Estimating Size
Funct ion Point s GUI Elem ent s
© What by Phymata
2008 Size, Features Size, Features
Solutions Inc.M L
Size S SM L
St age Early-Middle
(Everett Toews) Early
Thisyle
St presentation may
Seq. Seq.
Accuracy High Low
not be modified in
any way.
Permission to use this in size estimation
 Role of LOC
presentation isdimension
 Single
granted to
eWorld ES Inc. measure something
 Have to
provided this
copyright notice is
included.

40. Estimating Size
©  Function Points
2008 by Phymata
Solutions Inc.
(Everett External Inputs, External Outputs, External

Toews)
Queries, Internal Logical Files, External
This presentation may
not be modified in Files
Interface
any way.
 GUI Elements
Permission to use this
 Screens, Reports, Files, Interfaces, Dialogs
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

41. Estimating Effort
I nf ormal Comparison Est imat ion I ndust ry Average
© 2008 by oPhymata ect s
t Past Proj Sof t w are Tools Ef f ort Graphs
Solutions Effort
What Inc. Effort Effort
Size SM SM L SM
(Everett Toews)
St age Early-Middle Early-Middle Early
This presentation may
St yle Iter. & Seq. Iter. & Seq. Seq.
not be modified in
Accuracy Medium High Low-Medium
any way.
 Informal Comparison
Permission to use this
presentation is
 Estimation Software Tools
granted to
eWorld ES Inc. Average Effort Graphs
 Industry
provided this
copyright notice is
included.

42. Estimating Schedule
The Basic Schedule I nf orm al Est im at ion Sof t w are
Equation Com parison t o Past Tools
What Schedule
© 2008 by Phymata Schedule Schedule
Size ML SM L ML
Solutions Early
St age Inc. Early Early
(Everett Toews)
St yle Seq. Iter. & Seq. Iter. & Seq.
Accuracy Medium
This presentation may Medium High
not be modified in Schedule Equation
 The Basic
any way.ScheduleInMonths = 3.0 x StaffMonths1/3

Permission to use this
 Informal Comparison to Past Projects
presentation is
 EstimatedSchedule = PastSchedule x
granted to
(EstimatedEffort / PastEffort)1/3
eWorld ES Inc.
 Estimation Software Tools
provided this
copyright notice is
included.

43. Schedule Compression
 Shortening the schedule increases effort
©2008 by Phymata
Trade Offs
Solutions Inc.
(Everett Schedule | Effort

Toews)
This presentation may+100%
 -15% |
not be -10% | +50%
modified in
any way.
Permission to use this+25%
 -5% |
0%
presentation is
 | 0%
 Team Size
granted to
eWorld ES Inc.
providedAverageTeamSize = EffortEstimate /

this
Schedule
copyright notice is
included.

44. Estimating Planning Parameters
©  Estimating total activity
2008 by Phymata
Solutions Inc.
 Converting estimated effort to
(Everett Toews) planned
effort
This presentation may
not be modified in
 Estimating defect production and removal
any way.
Permission to use this
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

45. Estimate Presentation Styles
©  Communicate estimate assumptions
2008 by Phymata
Solutions Inc.
 Expressing uncertainty
(Everett Toews)
This presentation may
 Risk qualification
not be modified in
 Accuracy
any way.
Permission to use this
 Ranges
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

46. Politics, Negotiation and
Problem Solving
©  External constraints
2008 by Phymata
Solutions Inc.
 Negotiating a commitment
(Everett Toews)
This presentation may
 Problem solving
not be modified in
any way.Separate the people from the problem

Permission to use this
 Focus on interests, not positions
presentation is
 Invent options for mutual gain
granted to
eWorld ES Inc. on using objective criteria
 Insist
provided this
copyright notice is
included.

47. Outstanding Issues
©  Counting lines of code
2008 by Phymata
Solutions Inc.
 Estimates vs actual
(Everett Toews)
This presentation may
 Contractual software development
not be modified in
any way.
Permission to use this
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.

48. Recommendations
 Developers
 Use ranges
© 2008 by Phymata
Solutions Inc.
 Present estimates with assumptions
(Everett Toews)
 Management
This presentation may
not be Use historical data
modified in
any way.Archive estimates in an easily accessible place

Permission to usea standardized estimation procedure
 Publish this
presentation is
 Both
granted to
 Use checklists
eWorld ES Inc.
providedphymata.blogspot.com
 this
copyright notice is
included.

49. Conclusion
©  What am I doing about it?
2008 by Phymata
Solutions Inc.
(Everett Toews) next?
 What’s
This presentation may
 construx.com/Page.aspx?nid=297
not be modified in
any way.
Permission to use this
presentation is
granted to
eWorld ES Inc.
provided this
copyright notice is
included.