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Introduction to Software Project
Estimation I (Overview)
Barry Schrag
Software Engineering Consultant
MCSD, MCAD, MCDBA
[email protected]
What Are Your Expectations
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From this class?
Introductions
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Your background
Reason for taking this workshop
An unusual fact to remember you by!
What we will learn
This course focuses on an overview of Software
Estimation knowledge to include the tools,
techniques, and key concepts used in estimating size
and effort on software projects. Class content,
including hands-on exercises, is designed to provide
team members and Project Managers with resources
and skills to more accurately apply estimating
techniques at various points in a software
engineering process and how to interpret the result,
reducing risk during the software engineering effort.
Prerequisite: Experience in the field of software
engineering or project management, or relevant
coursework/knowledge.
Info
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Breaks
Food
Facilities
Workshop Format
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Introduction
Exercise without tools
Break
Lines of Code Lesson
Function Point Lesson
Exercise applying Function Point technique
Break
Lessons learned
Software Project Definitions
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Successful:
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Challenged:
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The project is completed on time and on budget,
with all features and functions as specified
The project is completed and operational, but over
budget, late, and with fewer features and
functions that initially specified
Failed:
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The project is cancelled before completion, never
implemented, or scrapped following installation
Project Success is Rare
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2004:
2000:
1995:
1994:
15%
23%
40%
31%
failed,
failed,
failed,
failed,
51%
49%
33%
53%
challenged,
challenged,
challenged,
challenged,
Source: Randy Miller, Microsoft
34%
28%
27%
16%
succeeded
succeeded
succeeded
succeeded
Project Status
(Standish 2004)
Software Projects
Failed, 18%
Succeeded,
29%
Challenged,
53%
Overview
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Why care about estimates?
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Repeatability
Accuracy to a date
Manage resources and cost
FP standards group says: +-4%  12%
LOC estimation error is history
dependent +- 200% down to +-5%
with PSP/PROBE
What is an "estimate" ?
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Our Premise: Effort in hours from size
More accurate for your team/process
Do engineers estimate? Do architects?
Do scientists?
Size  Effort hours  Schedule
Cone of Uncertainty
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It is very large during requirements
It gets smaller as
you proceed
through your
process!
Scenario I
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Read Exercise 1 Initial Estimate
Solidify any questions and assumptions
Can you make an initial estimate in
hours? If not, make a guess!
If you can, estimate how many defects
there will be
Results
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What were your estimates?
What tools would you use to perform
this task?
Some facts help in estimation
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Organization
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Is there IT Support?
What is their current and
projected load?
Engineering team in place?
Engineering Methodology
System Specs
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OS Platform
Architecture
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Backend Database/File
System, etc…
Calculation rule specifics?
Report output method
/Architecture in place?
Retention rate of data?
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Quality Specification
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Sales
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Performance?
Concurrency?
Lead time
Pipleline already full?
Project Management
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Supplier lead time
Partner co-operation
Partner dependencies
Important for Estimation
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What quality is required
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How many defects are acceptable after release?
How many defects do we need to find?
What is our team size
What is our team productivity (do we know?)
How many hours is the team is available to
work on this project per day? 6? 8? 10?
Are vacation days scheduled?
An Estimator uses
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Product Specs (size only)
Team Size (size  effort)
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PSP uses a team size of 1
Hours available per day for work
(effort  schedule)
Days off (effort  schedule)
The Cone of Uncertainty
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What does it look like?
What percent of software projects are
on time and on budget? 29%
Where does estimation error come
from?
Guessing
Historical Analysis
Estimation Error
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Unknown specs account for 33% of
error (McConnell 2006)
Lost project hours account for error on
schedule estimation, not size
estimation
Remember
Size leads to Effort leads to Schedule
Scope Creep
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2% increase per calendar month in
design and coding phases (McConnell 2006)
From end of requirements to start of
coding phases chart: (Capers Jones, 2002)
Estimation Formula
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Effort in hours
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Size of Specs
Size of Team
How do we find the size of specs?
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Only two ways accepted as better than
guessing!
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Function Points
Lines of Code using PROBE in the PSP
Line of Code Definitions
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KLOC (thousands)
SLOC (source)
LOC
CLOC (commented)
NCLOC (non commented)
System Size: Lines of Code
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Review Table 1
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Read Reading 1
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The Paradox of Source Code Metrics
Lines of Code as a metric
Read Reading 2
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A Few Words about the PSP and PROBE
Size estimating LOC/PROBE
LOC PSP/PROBE defects
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A benefit of this method:
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30-100% of defects can be found before
first compile!
LOC Has Problems!
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No theoretical foundation
No relationship between lines of code
and program operation
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C = A+B;
C = *A + *B;
Complexity and errors can increase with
equal LOC
System Size: Lines of Code
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There is no standard way to measure
Wide range of estimates for a language
Visual Basic 15 to 41 LOC!
LOC counts can be easily misinterpreted and
misused.
Don’t mix LOC counts from different languages and
types of code (i.e. test support, product etc…)
You can generate almost any productivity number
you want by changing the way you count LOC.
Tools? Code Counter Pro
Can estimate ratio of Comment Lines per SLOC
Break
Be back in …. Next up Function Points
System Size: Function Points
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1979, A.J. Albrecht of IBM published a
Function Point metric as a
‘measure of software productivity’ or
unit of work.
An Ideal Size Measure Should
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Be
Be
Be
Be
Measurable
Accountable
Precise
Independent of the measurer
System Size: Function Points
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Albrecht considered five operations
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The inputs to the application
The outputs from it
Inquiries by users (define user)
The data files that would be updated by
the application
The interfaces to other applications
The generic application
Output simple data
Data values in
Application
Data store
Output Calculated data
Modern Function Points
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After research, empirical weighting factors
became a standard
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The number of inputs was weighted by 4
The Outputs by 5
Inquiries by 4
The data file updates by 10
The interfaces by 7
These weights change based on number of
data fields used by each operation
System Size: Function Points
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IFPUG (International Function Point Users
Group)
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COSMICON (COmmon Software Measurement
International CONsortium)
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FP ISO 20626:2003 www.ifpug.org
FFP ISO/IEC 19761:2003
http://www.cosmicon.com
FP measures size of an operation not the
direct complexity of algorithms
Abstracted from language or implementation
FP Defect Rates are Known
DEFECT ORIGINS
 Requirements
 Design
 Coding
 Documentation
 Bad Fixes
 TOTAL
Per FP
1.00
1.25
1.75
0.60
0.40
5.00
Generic Application
Data values in
External Input
Output simple data
Application
Data store
(Internal Logical Files)
Output Calculated data
External Outputs (EO)
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An elementary process in which derived
data passes across the boundary from
inside to outside the application
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A report where data is calculated is an
example
For elaborated definition see Glossary
External Inputs (EI)
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Is an elementary process in which data
crosses the boundary from outside to
inside the application
For elaborated definition see Glossary
External inQuiry (EQ)
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An elementary process with both input
and output components that result in
data retrieval from one or more internal
logical files and external interface files
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A report where data is pre-calculated is an
example
For elaborated definition see Glossary
Internal Logical Files (ILF)
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A group of logically related data within
the application boundary
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Storage location for the users profile, for
product, system control info…
For elaborated definition see Glossary
Rating Logical Files
External Interface Files (EIF)
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Data used for reference purposes which
resides entirely outside the application
and is maintained by another
application
This is an Internal Logical File for
another application
For elaborated definition see Glossary
EQ and EO
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IFPUG is very clear on the difference
between EQ and EO
EQ should NOT update an ILF, no
derived data is created and NO formula
or calculations should be performed i.e.
an EQ is only a query
May require a certified FPA to be sure!
Function Point Terms Diagram
Note About Terms
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There may be more than one of ANY of
the 5 FP operations
Often more than one ILF in even the
smallest project
Imagine one ILF for Users, another for
Invoice, Products, System Control data
FPA Exercise (Exercise I)
We want to build an internet based system which
signs up users who want service. The system will
record the user information. It will look up the
service price for the monthly payment and display
this to the user before they approve. It will use the
payment rates which are held in a legacy system.
Once this payment is calculated, it is stored with the
users data and is not re-calculated again. The
system must provide two reports; 1) a monthly report
which details the invoice for the user, and 2) an ondemand report for management which aggregates
the projected income across all signed up users for
the monthly period
Exercise I – How Many?
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Match these concepts to the exercise
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ILF (Internal Logical Files)
EIF (External Interface Files)
EI (External Input)
EO (External Output) -- calculated
EQ (External inQuiry) -- just a query
Exercise I - Calculate FP Count
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The number of External Inputs __*4= __
The External Outputs
__*5= __
External inQuiries
__*4= __
The Internal Logical Files
__*10= __
The External InterFaces
__*7= __
TOTAL FP Estimate
= __
TOTAL Defects Estimate = FP * 5
= __
Exercise I - Calculate FP Count
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The number of External Inputs 2*4= __
The External Outputs
2*5= __
External inQuiries
2*4= __
The Internal Logical Files
1*10= __
The External InterFaces
1*7= __
TOTAL FP Estimate
= __
TOTAL Defects Estimate = FP * 5 = __
Exercise I - Calculate FP count
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The number of External Inputs 2*4= 8
The External Outputs
2*5=10
External inQuiries
2*4= 8
The Internal Logical Files
1*10= 10
The External InterFaces
1*7= 7
TOTAL FP Estimate
= 43
TOTAL Defects Estimate = FP * 5 =215
Exercise I
TOTAL FP Estimate
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= 43
Note that this is an independent
measure of the SIZE of the counted
functionality!
Exercise I hours to release
TOTAL FP Estimate
= 43
EFFORT = FP * process efficiency
Now apply the variables - 516 hours to release = 43 unadjusted
function points * 12 hours/fp
 Note that 12 is a LOW estimate of
process efficiency
Note the Weighting Factors
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Weighting changes based on complexity
but for that use a certified FP analyst!
We will assume average complexity
Example: Data Elements, see counting
practices manual!
Using Agile process + FPA
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Agile: Analyze, Test, Code, Deliver
Agile FPA: Analyze, Measure, Test,
Code, Deliver
Use the count as an opportunity to
elaborate on the requirements
Track estimates over time
Historical Effort Estimation
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ISBSG (International Software Benchmarking
Standards Group)
Assumes Average Productivity
Staff Months = .425 * (FP Count ^ .488) *
(Maximum Team Size ^.697)
Assumes 132 project focused hours per staff
month
Assumes 3rd GL, calibrated by 600 projects
Historical Measurement
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Thousands of projects
Consistent sizing with FPA
Record of time for each activity
Trends emerge
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Some activities are not performed on every
project
Cost for the activity doesn’t vary based on
project type
Activities by Project Type
Activity
Requirements
Prototyping
Architecture
Project Plans
Initial Design
Detailed Design
Design Reviews
Coding
Reuse Acquisition
Package Purchase
Code Inspections
Independent verification and validation
Configuration Management
Integration
User Documentation
Unit Testing
Function Testing
Integration Testing
System Testing
Field Testing
Acceptance Testing
Independent Testing
Quality Assurance
Installation and Training
Project Management
Commonly Used Activities*
End User
X
X
X
MIS
X
X
X
X
X
X
X
X
X
X
5
Activity by Project Type
Outsource
Commercial
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
16
X
X
X
20
Systems
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
22
X
21
Military
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
25
National Average Productivity
Activity
Requirements
Prototyping
Architecture
Project Plans
Initial Design
Detailed Design
Design Reviews
Coding
Reuse Acquisition
Package Purchase
Code Inspections
Independent verification and validation
Configuration Management
Integration
User Documentation
Unit Testing
Function Testing
Integration Testing
System Testing
Field Testing
Acceptance Testing
Independent Testing
Quality Assurance
Installation and Training
Project Management
Total hours per Function Point
Minimum
Work Hours per FP
Mode
0.38
0.75
0.53
0.88
0.26
0.44
0.09
0.26
0.33
0.75
0.44
0.88
0.33
0.59
0.66
2.64
0.07
0.22
0.09
0.33
0.44
0.88
0.66
1.06
0.04
0.08
0.26
0.53
1.32
1.89
0.33
0.88
0.44
0.88
0.33
0.75
0.26
0.66
0.26
0.59
0.22
0.38
0.44
0.66
0.44
0.88
0.22
0.38
0.66
1.32
9.50
19.56
Maximum
2.64
5.28
1.32
0.66
2.64
5.28
1.76
8.80
0.33
0.38
1.76
1.76
0.13
0.88
6.60
1.89
5.28
1.76
1.32
1.76
1.76
1.32
4.40
0.88
8.80
69.39
EFFORT is Estimated by
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Wideband Delphi-consensus-based NO!
Perform organization calibration to get
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Hours per Function Point
Historical Data gets better over time
Estimation Influences Are
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Additive Error due to
Size  Effort hours  Schedule
Error in Size Estimate
Error in Effort Estimate
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Productivity changes due to
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New team size
Work tasks change
Hours available to work are altered
Estimation Techniques
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Function Points estimate size
independently, and can find effort hours
after one use
PSP/PROBE Proxy-based estimates
guess about a size to find the effort
hours, but get better over time
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See chart slide 24
Software Estimation Tools
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PSP/PROBE is an estimation tool
Function Points are an estimation tool
LOC counting can be automated, but is
only useful for comment lines and PSP
Function Points are not easy to
automate!
Estimation Procedures
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First Estimate Size
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Determine Productivity
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Count Function Points as a size measurement
Or estimate LOC using PSP/PROBE method
Hours/FP or Hours/LOC
Calibrate using local history
Total Effort Hours
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Size FP * Hours/FP
or
Use PSP/TSP/PROBE to determine total hours
Estimation Method Costs
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Function Point certification
PSP/TSP and PROBE training
Project Cost Estimation
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Effort x (Salary + Burden) = Cost
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COCOMO 82  COCOMOII (2000) 
F2COCOMO
Requirement phase and cost is not
estimated by any COCOMO method!
Assumes 152 hours project time/month
F2COCOMO see;

www.cs.uwaterloo.ca/~adcaine/f2cocomo.
pdf
Size Issues Using FP
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Little applicability to effort without
historical data
Some Standards are in place, ISO, IEEE
History is available using ISBSG
database
Size Issues Using LOC
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Problems applying it to different code bases
i.e.
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SQL Data Driven Applications
XML, XSLT, ASP, VBScript, Jscript , ASP.NET
No standards
Can’t convert between size models
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From LOC to FP or FP to LOC
NO!
Range of LOC/FP is too large to use!
Effort Estimation Issues
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Effort = Size * Productivity
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Productivity measured as hours/Function
Point
Use local productivity Data and ISBSG
averages
Team history and cohesion do affect
results
Main point - Record hours worked
Schedule Estimation Issues
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Support
Documentation
QA (How many defects do you want
removed?)
Change Requests which are implemented
Turnover
Team History
Record hours worked to do your next
estimate
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Process change
Process Change Issues
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About failure rates of metrics estimation
initiatives
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Steven Kan, 2000
Management buy-in is most critical!
Exercise II
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Read Exercise II in the handout and
perform a rough Function Point size
estimate using the information given
Derive hours to complete product using
12 hours per function point efficiency
Estimate defects in product using the
US standard of 5 defects per Function
Point
Scenario II -- what is critical?
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The user will be presented with a calendar
They may choose a date or a holiday
They will identify it with a label
They will then choose an email notification
This data is recorded in the database
The system will provide an email notification
Scenario II how many items?
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The user will be presented with a calendar
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They may choose a date or a holiday
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EI
This data is recorded in the database
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EI
They will then choose an email notification
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EI
They will identify it with a label
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Calendar Date ILF, EO
User Event ILF
The system will provide an email notification
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EO
Scenario II
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EI 3*4 = 12
EO 2*5 = 10
EQ 0 * 4 = 0
ILF 2 * 10 = 20
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We are still assuming average complexity!
TOTAL Unadjusted Function Points = 42
DEFECTS = 42 * 5 = 210
Exercise II hours to release
TOTAL FP Estimate
= 42
EFFORT = FP * process efficiency
Now apply the variables - 840 hours to release = 42
unadjusted function points * 20
hours/fp
 Remember that 20 is an average
estimate of process efficiency
Effort Analysis

FP count of SIZE is about equal
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Exercise I FP count = 43 about 516 hours
Exercise II FP count = 42 about 840 hours
Why is there a large hours difference?

Calibrate your process efficiency
What did we learn?
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Overview of Software Estimation
knowledge
Tools, techniques, and key concepts

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Size and Effort
Resources and skills to more accurately
apply estimating techniques
Conclusion
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Choose an estimating technique
Make it part of your process at each
step and for each change requested
It can reveal process efficiency
Track error over time and use to predict
cone of uncertainty in the next cycle
Conclusion -- Costs
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PSP training cost = 2 weeks (80 hours)
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After 2 hours of use, your team process is CMMi
Level 5
TSP training is available for managers
Function Point certification costs = 2 days
(16 hours)
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Will help if you keep history between projects
No projections about CMMi level
Follow On Course
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Function Point Analysis Certification
PSP Training
Be sure to write it in your course
evaluation if you are inclined to work
toward either certification