IS estimating issues

1
IS estimating issues

• Unique projects with much innovation
• Estimates often produced early before
  specification agreed
• No professional estimators
• Few published metrics available

2
Analogy method

• Find a similar project
• Type of business
• Size of applications
• Scope of systems
• Technical methods and standards
• Must adjust for
• Organisational culture
• Users level of computer literacy
• Degree of management support for project

3
Analysis and programming approaches

• Explicitly estimate for one stage
• Analysis method analysis stage
• Programming method code/unit test stage
• Extrapolate whole project outcome from stage
  estimate
• Must adjust for
• Project size
• Familiarity with business and technical
  environment
• Technical complexity

4
Direct estimate (from project breakdown)

• Break down project (either using WBS or PBS
  approach)
• Estimate for each task / product
• Sum products to get stages
• Sum stages to get project
• Takes time
• and requires expert estimators

5
Delphi technique

• Several estimators given specification of work
  and asked for estimates
• Summarised anonymously and results circulated to
  estimators
• Can revise estimates in the light of others
  ideas
• Method reduces personal disagreements and
  ego-based issues

6
CoCoMo

• Formulae based on thousands of delivered source
  instructions (KDSI)
• Basic, intermediate and detailed versions
• CoCoMo II now developed for wider range of
  development approaches
• Useful elapsed time formula

2.5 x (estimated effort in man-months)0.33
7
Function point analysis

• Based on analysis of inputs, outputs and files
  accessed in system
• Starts with unadjusted function points
• Then adjusts for
• technical complexity
• performance-influencing factors
• risks

8
Supporting activities

• Can considerably inflate base estimates
• Includes
• Proportional activities
• Team leading/supervision
• Documentation
• Quality control
• Customer reviews
• Elapsed-time activities
• Project management
• Systems management
• Configuration management
• Project office work