| Apportionment | Costs allocated to a specific segment of a project by using a percentage of planned total cost—for example, framing a house might use 25 percent of the total cost, or coding a teaching module 40 percent of total cost.
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| Bottom-up estimates | Detailed estimates of work packages usually made by those who are most familiar with the task (also called micro estimates).
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| Delphi Method | A group method to predict future events—e.g., time, cost.
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| Direct costs | Costs that are clearly charged to a specific work package—usually labor, materials, or equipment.
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| Function points | Points derived from past software projects to estimate project time and cost, given specific features of the project.
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| Learning curves | A mathematical curve used to predict a pattern of time reduction as a task is performed over and over.
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| Overhead costs | Typically organization costs that are not directly linked to a specific project. These costs cover general expenses such as upper management, legal, market promotion, and accounting. Overhead costs are usually charged per unit of time or as a percentage of labor or material costs.
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| Padding estimates | Adding a safety factor to a time or cost estimate to ensure the estimate is met when the project is executed.
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| Phase estimating | This estimating method begins with a macro estimate for the project and then refines estimates for phases of the project as it is implemented.
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| Range estimating | An estimating procedure used when there is significant uncertainty regarding the cost or time to complete a specific activity. Individuals estimate the worst case, best case , and most likely cost or time for a specific activity to determine the range of costs and times (i.e. activity A should take 4 days but it could take between 2 and 7 days to complete).
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| Ratio methods | Uses the ratio of past actual costs for similar work to estimate the cost for a potential project. This macro method of forecasting cost does not provide a sound basis for project cost control since it does not recognize differences among projects.
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| Template method | Use of a prepared form to develop project networks, costs, and time estimates.
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| Reference Class Forecasting | A sophisticated forecasting method in which you take an external view and forecast project costs based on actual outcomes of similar projects.
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| Time and cost databases | Collection of actual versus estimated times and costs of work packages over many projects that are used for estimating new project tasks and their expected possible error.
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| Top-down estimates | Rough estimates that use surrogates to estimate project time and cost (also called macro estimates).
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