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6.3 Activity Duration Estimating


Activity duration estimating involves assessing the number of work periods likely to be needed to complete each identified activity. The person or group on the project team who is most familiar with the nature of a specific activity should make or at least approve the estimate.


6.3.1 Inputs

  1. Activity list
  2. Constraints
  3. Assumptions
  4. Resource requirements
  5. Resource capabilities
  6. Historical information

6.3.2 Tools & Techniques

  1. Expert judgement
  2. Analogous estimating
  3. Simulation

6.3.3 Outputs

  1. Activity duration estimates
  2. Basis of estimates
  3. Activity list updates






6.3.1 Activity Duration Estimating - Inputs Activity list

Refer to Activity list. Constraints

Refer to Constraints. Resource requirements

Refer to resource requirements. The duration of most activities will be significantly influenced by the resources assigned to them. Resource capabilities

The duration of most activities will be significantly influenced by the capabilities of the human and material resources assigned to them. For example, a senior staff member can generally be expected to complete a given activity in less time than a junior staff member. Historical information

Historical information on the likely duration of most activities is often available from:


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6.3.2 Activity Duration Estimating - Tools and Techniques Expert judgement

Durations are often difficult to estimate because of the number of factors which can influence them. (e.g resource levels, resource productivity). Expert judgement should be used wherever possible. Analogous estimating

Also called top-down estimating means using the actual duration of a previous similar activity as the basis for estimating the duration of a future activity. It is frequently used when there is limited amount of detailed information about the project. Simulation

Simulation involves calculating multiple durations with different sets of assumptions. The most common is Monte Carlo analysis in which a distribution of probable results is defined for each activity and used to calculate a distribution of probable results for the project.


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6.3.3 Activity Duration Estimating - Outputs Activity duration estimates

These are quantifiable assessments of the likely number of work periods that will be required to complete an activity. Activity duration estimates should also include some indication of the range of possible results. Basis of estimates

Assumptions made in developing estimates must be documented. Activity list updates

Refer to activity list updates.


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