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Estimating Project Times and Costs - Coggle Diagram
Estimating Project Times and Costs
Factors influencing the Quality of Estimates
Planning Horizon
Project Complexity
People
Project Structure and Organization
Padding Estimates
Organization Culture
Other factors
Estimating Guidelines for Times, Costs, and Resources
Top-Down versus Bottom-Up Estimating
Top-Down
Consensus
Based on previous effort and experience estimate project
Delphi Method
Ratio Methods
Use ratio of previous data
Apportion
Apportionment is used when projects
closely follow past projects in features and costs.
Methods for Software projects
Learning Curves
Differences
Top-Down Estimates
Usually derived from someone who uses experience and/or information to determine the project duration and total cost.
Made by top managers who have limited knowledge of the details needed to complete the project.
Bottom-Up Approach
Can serve as a check on cost elements in the WBS by rolling up the work packages and associated cost accounts to major deliverables at the work package level.
Bottom-Up
Template Methods
Parameteric Procedures Applied to Specific Task
Range Estimating
A Hybrid: Phase Estimating
Methods for Estimating Project Times and Costs
Level of Detail
Level of detail is different for different levels of management
At any level the detail
should be no more than is necessary and sufficient.
Type of Costs
Direct Costs
Direct Project Overhead Costs
General & Administrative (GA) Overhead Costs
Refining Estimates
Interaction costs are hidden in estimates
Normal condition do not apply
Things go wrong on projects
Changes in project scope and plans
Overly Optimistic
Strategic misinterpretation
Creating a Database for Extimating
The best way to improve estimates is to collect and archive data on past project estimates and actuals.
Saving historical data—estimates and actuals—provides a knowledge base for improving project time and cost estimating
Creating an estimating database is a “best practice” among leading project management organizations.