Rapid Development Chapter 8 Estimation

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Rapid DevelopmentChapter 8Estimation
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Chapter 8

• The Software-Estimation Story
• Software and Construction
• Software Development as a Process of Refinement
• Amount of Refinement Possible

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Chapter 8
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Chapter 8

• The Software-Estimation Story
• Estimation vs. Control
• Cooperation
• Convergence Between Estimates and Reality
• The Estimation Story in a Nutshell
• Accuracy vs. Precision

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Chapter 8

• Estimation-Process Overview
• Estimate the Size of the Product (SLOC, function
  points)
• Estimate the Effort (man-months)
• Estimate the Schedule (calendar months)
• Provide estimates in ranges and periodically
  refine the ranges to provide increasing precision
  as the project progresses

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Chapter 8

• Size Estimation
• Algorithmic Approach
• Size Estimation Software
• Historical Data from Similar Project
• Function Point Estimation
• Inputs
• Outputs
• Inquiries
• Logical Internal Files
• External Interface Files
• (Table Formulas)

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Chapter 8

• Estimation Tips
• Avoid off-the-cuff estimates
• Allow time for the estimate, and plan it
• Use data from previous projects
• Use developer-based estimates
• Estimate by walk-through
• Estimate by categories
• Estimate at a low level of detail
• Dont omit common tasks
• Use software estimation tools
• Use several different estimation techniques, and
  compare the results
• Change estimation practices as the project
  progresses

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Chapter 8

• Estimate Presentation Styles
• Plus-or-minus qualifiers
• Ranges
• Risk quantification
• Cases (Best, planned, current, worst)
• Coarse dates and time periods
• Confidence factors

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Chapter 8

• Effort Estimation
• Use estimation software to create an effort
  estimate directly from the size estimate
• Use the schedule tables to convert SLOC to effort
• Use historical data
• Use algorithmic approach

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Chapter 8

• Schedule Estimation
• Equation
• schedule in months 3.0 man-months1/3
• Commitment-based Scheduling
• Jones First-Order Estimation Practice

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Chapter 8

• Ballpark Schedule Estimates
• Background
• Schedules (Calendar months)
• Efforts (Man-Months)
• System sizes (SLOC)
• Small projects ( gt 10,000 SLOC )
• Lines of code vs Function Points
• Accuracy of the estimates

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Chapter 8

• Shortest Possible Schedules
• Assumptions
• Staffing
• Management
• Tool Support
• Methodology
• Compression
• Two facts of life
• There is a shortest possible schedule, and you
  cant beat it
• Costs increase rapidly when you shorten the
  schedule below nominal

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Chapter 8

• Schedule compression factor desired schedule /
  initial schedule
• Compressed schedule effort initial effort /
  schedule compression factor
• Efficient Schedules
• Assumptions
• Relationship between shortest possible
  efficient schedules
• Nominal Schedules
• Assumptions
• Why develop efficiently?
• What to do first with the Ballpark Schedules

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Chapter 8

• Estimate Refinement
• Initial single-point estimate mistake
• Point in Project
  Estimate(mm)
• Initial Product concept 100
• Approved product concept 100
• Requirements Specification 135
• Product Design Specification 145
• Detailed Design Specification 160
• Final 170

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Chapter 8

• Range Estimation History
• Point in Project
  Estimate(mm)
• Initial Product concept 25 - 400
• Approved product concept 50 - 200
• Requirements Specification 90 - 200
• Product Design Specification 120 - 180
• Detailed Design Specification 145 - 180
• Final 170

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Chapter 8

• Recalibration
• Suppose you miss 1st milestone by 25,
• Assume you can make up the lost week later in
  schedule?
• Add the week to the total schedule?
• Multiply the whole schedule by magnitude of the
  slip?

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Chapter 8

• Application
• We want to develop a 250,000 LOC business
  product. How much effort can we save if we can
  improve our process from Nominal to Efficient?
• We are developing a 120 KLOC systems program.
  Our estimate for initial schedule is 28 months
  for nominal development. What are the schedule
  compression factors, assuming a shortest possible
  schedule and an efficient schedule, respectively?

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Chapter 8

• Application (cont.)
• Looking at function point estimates, if we have
  an estimate of 600 function points for a
  business software, and our company is
  considered worst in class, using Table 8.7, what
  is the estimated schedule in months?
• The last two shrink-wrap products our company had
  developed were about 80 KLOC and took around 14
  months to complete. On our next project, a
  similar product, our boss wants the same sized
  product done in 9 months, what is your response?

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Chapter 8

• Summary