1. Cost Estimation
Two days. Need to do the function point counting. Not sure cocomo is useful unless we show the actual parameters and have the estimate costs. Might be useful to do this at the end of SEI.

2. Cost Estimation
“The most unsuccessful three years in the education of cost estimators appears to be fifth-grade arithmetic.
Norman R. Augustine

3. Goal
The cost estimation community is working to improve estimations so that sophisticated organizations can produce products with 5% of the estimated cost (instead of 10%).

4. Goal
The cost estimation community is working to improve estimations so that sophisticated organizations can produce products with 5% of the estimated cost (instead of 10%).
The typical software organization struggles to avoid estimates that are incorrect by 100%.

5. Goal What does “incorrect by 100%” mean?
The cost estimation community is working to improve estimations so that sophisticated organizations can produce products with 5% of the estimated cost (instead of 10%).
The typical software organization struggles to avoid estimates that are incorrect by 100%.

6. Requirements for Estimations
What are cost estimates used for?

7. Requirements for Estimations
What are cost estimates used for?
What are the important characteristics of a cost estimate?

8. Requirements for Estimation
Timely
It is of limited value to provide the estimate after the project is complete
How early?

9. Requirements for Estimation
Timely
It is of limited value to provide the estimate after the project is complete
How early?
Before implementation
Before complete design
Maybe before complete requirements

10. Requirements for Estimation
Timely
It is of limited value to provide the estimate after the project is complete
Accurate
How accurate is enough?

11. Requirements for Estimation
Timely
It is of limited value to provide the estimate after the project is complete
Accurate
How accurate is enough?
Enough for planning, bidding, scheduling

12. Scenario
A typical software development shop. A boss is speaking with the lead developer.
(I need two volunteers to play these parts.)
Get two students to play these parts

13. Scenario
What’s up with the boss?

14. Scenario What’s up with the boss?
What does the boss think about the employee?

15. Problem with Scenario 1
The boss wasn’t asking for an estimate. The boss was asking for a plan to hit the target.
Your boss may or may not know the difference.

16. Scenario 2
Same two students?

17. Scenario 2
What’s the difference?

18. Definitions
Estimate
Target
Commitment
Plan

19. Estimate 1. A tentative evaluation or rough calculation.
2. A preliminary calculation of the cost of a project.
3. A judgment base upon one’s impressions; opinion
American Heritage Dictionary, 2nd Ed. 1985

20. Targets
“We need to have the prototype ready by the end of the semester.”
“These functions should be implemented by August 30 when the contract ends.”
“The cost of the project is limited to $250,000, because that’s the maximum budget.”
“We have to ship 7.0 by second quarter next year, because I have a reunion to attend in July.”

21. Commitment Target: description of a desirable business objective
Commitment: a promise to deliver defined functionality at a specific level of quality by a certain date
Plan: a sequence of steps to achieve a goal (may include a schedule)

22. Terms
Note that target, estimate, and commitment are not the same concept, and the dates given for these may differ.

23. Scenario 3
Suppose I give an estimate of 90 days.
What does this mean?

24. Scenario 3 Suppose I give an estimate of 90 days. What does this mean?
This says there is a 100% probability of delivering on this schedule.
In order for the number to have value, we need to know what the variance is.
How likely are we to hit this estimate?
(Usually, this is a target, not an estimate.)
Scenario 3
Suppose I give an estimate of 90 days.
What does this mean?

25. Scenario 3: Bell curve
What does it mean?
Is this more accurate?

26. What assumptions does this make?
Scenario 3: Bell curve
What assumptions does this make?
What does it mean?
Is this more accurate?
It assumes that you are equally likely to finish early as opposed to late

27. Scenario 3: Realistic What does this mean? Why is it shaped that way?
There’s a limit to how well things can go, but no limit to how badly they can go.

28. Quiz Take the quiz. Rotate papers Grade quiz Report grades
Put in spreadsheet
Explain the probability distribution for 90%

29. Answers 1 Surface Temperature of the Sun 10,000 F /6,000 C 2
Latitude of Shanghai
31 degrees North 3
Area of Asian continent
17,139,000 square miles
44,390,000 sq Km 4
Birth year of Alexander the Great
356 BC 5
Total value of U.S. currency in circulation in 2004 (in U.S. dollars)
$719,900,000,000
($720 billion) 6
Total volume of the Great Lakes
1.8 *10*23 U.S. gallons
6.8*10^23 liters 7
World wide box office receipts for the movie Titanic as of 2006
$1.835 billion 8
Total length of the coastline of the Pacific Ocean
84,300 miles /135,663 Km 9
Number of books published in U.S. since 1776
22 million 10
Weight of heaviest blue whale on record
380,000 pounds
179,000 Kg

30. Scores How many with 10 correct? 9? 8? 7? …. (plot in excel)
(show with normal distribution)
(Show with expected distribution)

31. Math of the expected distribution
If we have a 90% probability for any single answer, then:
Probability of getting all 10 correct: .9^10 = 34.9%
Probability of getting 9 correct: (.9^9*.1)*10 = 38.7%
8: ^8*.1^2*45 = 19.4%
For any given combination, .9^8*.1^2. But there are 45 different ways to put two wrong in a list of 10.
You can put the first wrong answer in any one of the first 9 places.
If you put it in the first spot, there are 9 places to put the second.
If you put it in the second spot, there are 8 places for the second.
And so on.
… + 1
… + 9
9*10 = 2x, x = 45.
For any given combination, .9^8*.1^2. But there are 45 different ways to put two wrong in a list of 10.
You can put the first wrong answer in any one of the first 9 places.
If you put it in the first spot, there are 9 places to put the second.
If you put it in the second spot, there are 8 places for the second.
And so on.
… + 1
… + 9
9*10 = 2x, x = 45.

32. Math of the expected distribution
If we have a 90% probability for any single answer, then:
Probability of getting all 10 correct: .9^10 = 34.9%
Probability of getting 9 correct: (.9^9*.1)*10 = 38.7%
8: ^8*.1^2*45 = 19.4%
For any given combination, .9^8*.1^2. But there are 45 different ways to put two wrong in a list of 10.
You can put the first wrong answer in any one of the first 9 places.
If you put it in the first spot, there are 9 places to put the second.
If you put it in the second spot, there are 8 places for the second.
And so on.
… + 1
… + 9
9*10 = 2x, x = 45.
Conclusion: with a 90% confidence, you have a 93% chance of getting 8 or more correct.
For any given combination, .9^8*.1^2. But there are 45 different ways to put two wrong in a list of 10.
You can put the first wrong answer in any one of the first 9 places.
If you put it in the first spot, there are 9 places to put the second.
If you put it in the second spot, there are 8 places for the second.
And so on.
… + 1
… + 9
9*10 = 2x, x = 45. 32

33. What we expect at 90% confidence
Historical data
Us last year

34. Questions:
Did you feel pressure to make your ranges wider? Or narrower? (Why?)

35. Questions:
Did you feel pressure to make your ranges wider? Or narrower? (Why?)
Where did the pressure come from?

36. Questions:
Did you feel pressure to make your ranges wider? Or narrower? (Why?)
Where did the pressure come from?
Is estimating the volume of the Great Lakes anything like estimating software?

37. Questions:
Did you feel pressure to make your ranges wider? Or narrower? (Why?)
Where did the pressure come from?
Is estimating the volume of the Great Lakes anything like estimating the impact of new programming tools on productivity, the productivity of an unidentified person, or the cost of developing software with no specification?

38. Accuracy and the cost of inaccuracy
What is the cost of overestimating?

39. Accuracy and the cost of inaccuracy
What is the cost of overestimating?
Parkinson’s Law: work expands to fill the time available
Goldratt’s Syndrome: People procrastinate until the last moment to start

40. Accuracy and the cost of inaccuracy
What is the cost of underestimating?

41. Accuracy and the cost of inaccuracy
What is the cost of underestimating?
Reduced effectiveness of project plans
Reduced chance of on-time completion
Poor technical approaches: Not enough time in requirements and design
Destructive late project dynamics
More status meetings
Interim releases
Fixing problems from workarounds

42. Cost Estimation 2

43. Recall cost estimation:
Sophisticated organizations: within 10%
Typical software organization: >100%
Estimates need to be timely and accurate
Estimate, Target, Commitment, Plan
Costs associated with overestimates
Costs associated with underestimates

44. How are we doing? KSLOC is 1,000 lines of source code
MSLOC is 1,000,000 lines of source code
With your partner, what does this graph say?

45. Benefits of Accurate Estimates
Improved status visibility
Higher quality
Better coordination with non-software functions
Better budgeting
Increased credibility for team
Early risk information

46. Benefits of Accurate Estimates
Improved status visibility
Track progress by comparing actual to planned
Ability to make a plan
Higher quality
Better coordination with non-software functions
Better budgeting
Increased credibility for team
Early risk information

47. Benefits of Accurate Estimates
Improved status visibility
Higher quality
Less stress on developers
Schedule pressure can increase defect rate by 400% (Jones 1994)
Better coordination with non-software functions
Better budgeting
Increased credibility for team
Early risk information

48. Benefits of Accurate Estimates
Improved status visibility
Higher quality
Better coordination with non-software functions
Testing, documentation, marketing, training, support
Better estimation: tighter coordination
Better budgeting
Increased credibility for team
Early risk information

49. Benefits of Accurate Estimates
Improved status visibility
Higher quality
Better coordination with non-software functions
Better budgeting
obvious
Increased credibility for team
Early risk information

50. Benefits of Accurate Estimates
Improved status visibility
Higher quality
Better coordination with non-software functions
Better budgeting
Increased credibility for team
Not unusual for
team to estimate,
others (manages, marketers, sales staff) turn it into optimistic business target
Developers overrun
Others blame team
Early risk information

51. Benefits of Accurate Estimates
Improved status visibility
Higher quality
Better coordination with non-software functions
Better budgeting
Increased credibility for team
Early risk information
If target and estimate don’t match, then opportunity to:
fix problem (reassign resources)
Re-scope
Cancel

52. Approaches to arriving at a number
Count
Compute
Judge

53. Approaches to arriving at a number
Count
If you want to know how many people in the room, count them
Usually not possible (e.g., how many people are on Earth?)
Compute
Judge

54. Approaches to arriving at a number
Count
Compute
Find some approach
E.g., Count the number of jelly beans in 1” and use that to compute the total number in the jar
Judge

55. Approaches to arriving at a number
Count
Compute
Judge
a.k.a. “guess”

56. Counting vs. Estimating
Similarities:
Differences:

57. Counting vs. Estimating
Similarities:
Both arrive at a number representing some real value
Both are subject to error
Differences:
Estimating implies imprecise knowledge

58. Proxy A value that is used to represent some other value
Example: Estimate the weight of the people in the airplane from the number of people in the airplane (requires that we also know the average weight of people)

59. 1 minute drill
What is it that we want to estimate in software?

60. Things we want to estimate in software
Cost
Resources
Revenue

61. 1 minute drill: What are proxies for these?
Cost
Resources
Revenue

62. Proxies in software estimation
Cost
Program size
Program complexity
Development time
Resources
Number of users
Revenue
Number of customers

63. Sources of uncertainty
Inaccurate information about project
Inaccurate information about ability of project team
Too much chaos in project
Inaccuracies in estimation process

64. Group Review Estimates
Individually:
Read the assignment for the movie rental program.
Predict the cost (time) to develop the code.
Put the time estimate on the card and turn it in.

65. Group Review Estimate: Team
In groups of 4: Compare estimates.
Discuss the differences enough to understand the sources of the differences.
Work until you reach consensus on the high and low ends of the estimation ranges
You cannot just “average” the estimates.
You must reach consensus on the estimate. Discuss until you get buy-in from the entire group.
Turn in the results of this exercise.

66. Wideband Delphi Estimators prepare initial estimates
The estimators meet with a coordinator to discuss estimation issues
Estimators give their estimates to the coordinator anonymously
The estimates are summarized on an iteration form
Estimators meet to discuss differences
Estimators vote to accept the average. If any votes “no”, return to step 2

67. Wideband Delphi Votes and estimates are anonymous
Reduces political pressure
Coordinator must prevent dominant personalities from controlling discussions
(Frequently, the most reserved person has the best insights)

68. Results of Wideband Delphi
Estimation error cut by 40% compared to initial group average
Accuracy improves in 80% of the cases
Useful for early estimates, particularly with unfamiliar systems
Not so useful for detailed estimates

69. LOC, SLOC, KSLOC, MSLOC Lines of code Standard measure of size
Often a measure of cost (i.e., time)

70. What assumptions does this make?
LOC, SLOC, KSLOC, MSLOC
Lines of code
Standard measure of size
Often a measure of cost (i.e., time)
What assumptions does this make?

71. Function Points
Synthetic measure of program size used to estimate size early in the project
Easier (than lines of code) to calculate from requirements
Standards at the International Function Point Users Group (IFPUG)

72. FP Rules: #FPs depends on:
External Inputs
External Outputs
External Queries
Internal Logical Files
External Interface Files

73. FP Rules: #FPs depends on:
External Inputs
Data entering the system
Screens, forms, dialogs, controls
User or other program adds, deletes, modifies data
Any input that requires processing logic
External Outputs
External Queries
Internal Logical Files
External Interface Files

74. FP Rules: #FPs depends on:
External Inputs
External Outputs
Derived Data leaving the system
Screens, reports, dialog boxes, control signals generated for end user or other program
External Queries
Internal Logical Files
External Interface Files

75. FP Rules: #FPs depends on:
External Inputs
External Outputs
External Queries
Base data leaving the system
I/O combinations in which an input results in a simple output
Queries retrieve data with no formatting. Output is formatted
Internal Logical Files
External Interface Files

76. FP Rules: #FPs depends on:
External Inputs
External Outputs
External Queries
Internal Logical Files
Data maintained within the application
Major logical groups of end-user data completely controlled by the program
Might be a flat file, a database table, or a collection of other data
External Interface Files

77. FP Rules: #FPs depends on:
External Inputs
External Outputs
External Queries
Internal Logical Files
External Interface Files
Data maintained outside the application
Files controlled by other programs

78. Function Points Complexity
The complexity of each function point depends on:
Record Element Types (RETs)
Data Element Types (DETs)
File Types Referenced (FTRs)

79. Function Points Complexity
The complexity of each function point depends on:
Record Element Types (RETs)
a user recognizable subgroup of data elements within an ILF or EIF
Data Element Types (DETs)
File Types Referenced (FTRs)

80. Function Points Complexity
The complexity of each function point depends on:
Record Element Types (RETs)
Data Element Types (DETs)
a unique user recognizable, non-recursive field
File Types Referenced (FTRs)
If a DET is recursive then only the first
occurrence of the DET is considered not every occurrence.

81. Function Points Complexity
The complexity of each function point depends on:
Record Element Types (RETs)
Data Element Types (DETs)
File Types Referenced (FTRs)
a file type referenced by a transaction. An FTR must also be an internal logical file or external interface file
All the of the components are given a complexity level based on RET’s FTR’s and DETs:
EI,EO, &EQ are based on FTRs and DETs. EIF & ILF are based on RETs and DETs.

82. Complexity Table- External Inputs (EI)

83. Complexity Table- External Outputs (EO) & Inquiries (EQ)

84. Complexity Table- Internal Logical File (ILF) & External Interface File (EIF)

85. FP Rules: Complexity Multipliers
Low Complexity
Medium Complexity
High Complexity
External Inputs 3 4 6
External Outputs 5 7
External Queries
Internal Logical Files 10 15
External Interface Files
These are the non-adjusted function point values…

86. Value Adjustment Factor
It is based on 14 general system characteristics that rate the functionality of the application
Performance, End-user efficiency, Reusability…
Each characteristic is assigned a degree of influence range on a scale from 0 to 5
A formula is then used to account for these characteristics

87. LOC vs FP (Boehm 2000, Stutzke 2005)
Language
LOC per FP
Ada 50 C
128 C# 55
C++
Java
Assembly
213
Perl 20 VB 32

88. FP results Certified counters vary by 10%
Untrained counters vary by much more
The multipliers may or may not be useful (some research indicates unadjusted FPs are more closely correlated with effort)
The LOC have on average a range of 3x wrt FPs

89. Function Point Counting Exercise
In your teams, compute the FPs for the voting system and answer the questions at the end of the of the exercise