6.4 Estimate Activity Durations

11/01/2020 by tvolodi

The process of estimating the number of work periods needed to complete individual activities with estimated resources.

The key benefit – it provides the amount of time each activity will take to complete.

Frequency: throughout the project.

Process name/ Enterprise Process Asset Group	Input	Process	Output	Process name/ Enterprise Process Asset Group
Project Management Plan	Schedule management plan	6.4 Estimate Activity Durations	Duration Estimates	Project Documents
	Scope baseline		Basis of estimates
Project Documents	Activity attributes		Activity attributes	Project document updates
	Activity list		Assumption log
	Assumption Log		Lesson learned register
	Lesson learned register
	Milestone list
	Project team assignments
	Resource breakdown structure
	Resource calendars
	Resource requirements
	Risk register
Enterprise environmental factors
Organizational process assets

Estimation of the amount of work effort + available resource (quantity and quality) estimation + project calendars + resource calendars -> approximate number of work periods (activity duration) .

Factors for consideration:

• Law of diminishing returns. Effect of using the next unit of resource is lesser than using the previous unit.
• Number of resources. Increasing the number of one resource not always reduce usage of others including time. Increased number of people leads to increased communications which lead to increased time to execute job.
• Advances in technology.
• Motivation of staff.
  • Student Syndrome – start to work before deadline;
  • Parkinson’s Law – work expands to fill the all available time.

6.4.1 Inputs

6.4.1.1 Project Management Plan

Used components:

• Schedule management plan. The used method and accuracy level, other criteria to estimate durations.
• Scope baseline. Used: WBS dictionary (technical details).

6.4.1.2 Project Documents

To consider:

• Activity attributes. Predecessor-successor relationships, lead and lags, logical relationships.
• Activity list. Contains all schedule activities for the project.
• Assumption log. Assumptions + constraints.
• Lesson learned register.
• Milestone list.
• Project team assignments.
• Resource breakdown structure. A hierarchical structure of the identified resources by category and type.
• Resource calendars. Availability of specific resource, resources with specific attributes.
• Resource requirements. Performance level, skill level, …
• Risk register.

6.4.1.3 Enterprise Environment Factors

Include:

• Duration estimating databases, other reference data,
• Productivity metrics,
• Published commercial information,
• Location of team member.

6.4.1.4 Organizational Process Assets

Include:

• Historical duration information,
• Project calendars,
• Estimating policies,
• Scheduling methodology,
• Lesson learned repository.

6.4.2 Tools and Techniques

6.4.2.1 Expert Judgement

By individuals or groups by topics:

• Schedule development, management and control;
• Expertise in estimating;
• Discipline or application knowledge.

6.4.2.2 Analogous Estimating

A technique for estimating the duration the duration or cost of an activity or a project using historical data from a similar activity or project. The activities / project should be analogous. For the duration it is taken actual duration. The method is frequently used when there is limited information about the project.

Less costly but less accurate.

6.4.2.3 Parametric Estimating

An algorithm is used to calculate cost or duration based on historical data and project parameters. A statistical relationship between historical data and other variables.

6.4.2.4 Three-Point Estimating

Defines an approximate range for an activity duration:

• Most likely (tM). The estimate for the most likely variant of resource number, quality, availability and so on.
• Optimistic (tO). Best-case scenario.
• Pessimistic (tP). The worst-case scenario.
• Expected (tE). tE = (tO+tM+tP)/3. Used when there is insufficient historical data or when using expert judgmental data.

6.4.2.5 Bottom-up Estimating

Estimating by aggregating the estimates of the lower-level components of the WBS.

The activity is decomposed to the needed level of detail to get a confident detail estimations.

6.4.2.6 Data Analysis

• Alternatives Analysis. Used to compare:
  • Various levels of resource capability or skills;
  • Scheduling compression techniques;
  • Different tools;
  • Decisions on make/rent/buy resources.
• Reserve analysis. Used to determine the amount of contingency and management reserves needed for the project. Duration estimates may include contingency reserve (schedule reserves) for schedule uncertainty for the identified risks that are accepted. The contingency reserve may be a percentage or a fixed number of work periods. They may be aggregated. With more precise information on the project the reserve may be used, reduced, or eliminated. The reserves should be clearly documented.
  • Management reserve is allocated for management control purposes -> unforeseen work that is within the scope of project. not included into the schedule baseline, but it is part of the overall project duration requirements. Use of the reserve may require a change to the schedule baseline.

6.4.2.7 Decision Making

Voting.

6.4.2.8 Meeting

6.4.3 Outputs

6.4.3.1 Duration Estimates

Quantitative assessment of the likely number of time periods that required to complete an activity, a phase, or a project. They do not include any lags. They may include the range of possible results.

6.4.3.2 Basis of Estimates

How the estimates were derived. May include:

• Documentation of the basis of the estimate,
• Documentation of all assumptions made,
• Documentation of any known constraints,
• Indication of the range of possible estimates to indicate that the duration is estimated between a range of values,
• Indication of the confidence level of the final estimate,
• Documentation of individual project risks influencing this estimate.

6.4.3.3 Project Documents Updates

Include:

• Activity attributes.
• Assumption log.
• Lesson learned register.