Estimating Activity Durations: Techniques and Tools for Accurate Scheduling

Estimating Activity Durations is a key process in Project Schedule Management, which involves predicting the amount of time each project activity will take to complete.

This section explores various techniques and tools used in estimating activity durations, including decision-making techniques, three-point estimating, analogous estimating, parametric estimating, expert judgment, data analysis techniques, meetings, and bottom-up estimating. These methods help in creating a realistic and accurate project schedule, considering factors such as resource capabilities, cost, duration variables, and potential risks.

Estimating activity durations interacts with other project management processes in several ways. For instance, the estimates generated during this process feed into the development of the project schedule and the project management plan. Similarly, the process of estimating activity durations is influenced by the project scope, as defined in the Work Breakdown Structure (WBS), and the available resources, as outlined in the resource management plan. Ultimately, accurate duration estimates contribute to effective project execution and successful project completion.

Learning Objectives

  • Understand the role of decision-making techniques, three-point estimates, and analogous and parametric estimating in project schedule management.
  • Recognize the importance of considering expertise, historical data, and project parameters in estimating activity durations.
  • Understand the concept and application of data analysis techniques, including alternatives analysis and reserve analysis, in estimating activity durations.
  • Recognize the role of meetings in estimating activity durations and the process of breaking down user stories into tasks in an agile approach.
  • Understand the concept of bottom-up estimating and how dependencies between activities can influence the application and use of resources.

Decision Making

In the intricate world of project management, decision-making techniques are the unsung heroes, particularly when it comes to estimating activity durations. These techniques, such as voting methods, serve as the backbone of consensus-building, guiding project teams towards unified decisions on various project aspects.

One such voting method is the "fist of five" technique, often used in agile-based projects. This technique is a quick and effective way to gauge team support for a decision. The project manager asks team members to show their level of support by raising a closed fist (indicating no support) to five fingers (indicating full support).

If a team member shows fewer than three fingers, it indicates some level of objection or concern. The project manager then gives these team members an opportunity to discuss their objections. This open discussion can lead to a better understanding of the issues at hand and can help the team find a more agreeable solution.

The fist of five process is a relentless pursuit of consensus, continuing until the team reaches a unanimous decision or agrees to advance to the next issue. This technique ensures every team member's voice echoes in the decision-making process, and their concerns are addressed before any forward movement. It's a beacon of transparency, collaboration, and consensus-building—cornerstones of effective project management.

Which of the following best describes the fist of five decision-making technique?
  1. A technique where team members vote by raising a number of fingers from one to five to indicate their level of support for a decision
  2. A technique where team members vote by raising their hand if they support a decision
  3. A technique where team members vote by writing their decision on a piece of paper
  4. A technique where team members vote by saying "yes" or "no" to a decision
A) A technique where team members vote by raising a number of fingers from one to five to indicate their level of support for a decision

Unlock Full Course Access

Take the next step in your career—purchase now and master project management with our comprehensive PMP exam prep course!

Three-Point Estimating

Three-point estimating is a valuable tool in project schedule management, particularly in improving the accuracy of single-point duration estimates by considering estimation uncertainty and risk. This technique helps define an approximate range for an activity’s duration, taking into account the most likely, optimistic, and pessimistic estimates.

The most likely estimate is based on the duration of the activity, considering factors such as resource allocation, productivity, availability, dependencies, and potential interruptions. The optimistic estimate, on the other hand, is based on the best-case scenario for the activity. Conversely, the pessimistic estimate considers the worst-case scenario.

The expected duration of a project can be calculated based on the assumed distribution of values within the range of these three estimates. This is often done using the triangular distribution, a formula commonly used when there is a lack of sufficient historical data or when judgmental data is being used. The formula "*tE* = (*tO* + *tM* + *tP*) / 3" is used to calculate the expected time for a task, where "*tE*" represents the expected time, "*tO*" stands for the optimistic time estimate, "*tM*" represents the most likely time estimate, and "*tP*" stands for the pessimistic time estimate.

Triangular distribution provides an expected duration and helps clarify the range of uncertainty around the expected duration. This technique is crucial in project schedule management as it allows for a more accurate and realistic estimation of activity durations, thereby enhancing the overall project planning and execution process.

What is the primary purpose of using three-point estimating in project schedule management?
  1. To provide a detailed cost estimate of the project
  2. To improve the accuracy of activity duration estimates by considering estimation uncertainty and risk
  3. To provide a detailed schedule of all project activities
  4. To record additional information on existing or new stakeholders
B) To improve the accuracy of activity duration estimates by considering estimation uncertainty and risk

Analogous Estimating

Analogous estimating is a technique used to estimate the duration or cost of an activity or a project based on historical data from similar activities or projects. It uses parameters from a previous, similar project, such as duration, budget, size, weight, and complexity, to estimate for a future project. When estimating durations, analogous estimating relies on the actual duration of previous, similar projects.

Analogous estimating is a gross value estimating approach, which can be adjusted for known differences in project complexity. It is often used to estimate project duration when detailed information about the project is limited. This technique is less costly and less time-consuming compared to other estimating methods, but it is also less accurate.

Analogous duration estimates can be used for the entire project or for specific segments of a project. It can be used alongside other estimating methods to increase accuracy and reliability. The reliability of analogous estimating increases when the previous activities are similar in reality and not just superficially. The project team members preparing the estimates should possess the necessary expertise for analogous estimating to be reliable.

What is analogous estimating in the context of project schedule management?
  1. A technique that uses the actual duration of previous, similar projects to estimate the duration of a future project
  2. A technique that uses the actual cost of previous, similar projects to estimate the cost of a future project
  3. A technique that uses the actual resources of previous, similar projects to estimate the resources of a future project
  4. A technique that uses the actual risks of previous, similar projects to estimate the risks of a future project
A) A technique that uses the actual duration of previous, similar projects to estimate the duration of a future project

Parametric Estimating

Parametric estimating is a technique used in project schedule management that leverages historical data and project parameters to calculate cost or duration. This technique uses a statistical relationship between historical data and other variables, such as square footage in construction projects, to estimate activity parameters like cost, budget, and duration.

In parametric estimating, durations are calculated quantitatively. For instance, the duration of a task can be determined by multiplying the amount of work to be done by the number of labor hours required per unit of work. In a design project, the duration can be estimated by multiplying the number of drawings by the number of labor hours needed per drawing. Similarly, in a cable installation project, the duration can be estimated by multiplying the meters of cable by the number of labor hours required per meter.

The capability of the assigned resource also influences the duration estimate in parametric estimating. For example, if a resource can install 25 meters of cable per hour, the duration to install a certain number of meters can be calculated using the formula: total meters of cable divided by the meters installed per hour by the resource.

The accuracy of parametric schedule estimates can be influenced by the sophistication of the model and the underlying data. These estimates can be applied to an entire project or to specific segments of a project, and can be used in combination with other estimating methods. This flexibility makes parametric estimating a valuable tool in project schedule management.

What is the primary purpose of parametric estimating in project management?
  1. To calculate cost or duration based on historical data and project parameters
  2. To provide a detailed schedule of all project activities
  3. To list all the stakeholders involved in a project
  4. To provide a detailed cost estimate of the project
A) To calculate cost or duration based on historical data and project parameters

Expert Judgment

Expert judgment in estimating activity durations is like a seasoned navigator charting a course, a key process in project schedule management. It involves leveraging the knowledge and experience of individuals or groups with specialized expertise, akin to a navigator's understanding of the seas, in schedule development, management, and control.

Specialized knowledge or training in estimating is particularly valuable in project management. Experts in this area can provide accurate and realistic duration estimates for project activities, contributing to the development of a feasible and reliable project schedule.

Discipline or application knowledge is another area where expertise should be considered in project management. Individuals or groups with in-depth knowledge in specific disciplines or applications can provide valuable insights into the intricacies of project activities, helping to refine duration estimates.

Just as a seasoned navigator's expertise can significantly enhance the accuracy of a voyage, involving individuals or groups with specialized knowledge or training in these areas in the process of estimating activity durations can significantly enhance the accuracy and reliability of the project schedule. Their expertise can help identify potential challenges, propose effective solutions, and ensure that the project schedule aligns with the project objectives and constraints, guiding the project safely to its destination.

Why is expertise important in the process of estimating activity durations in project management?
  1. It helps in identifying potential risks in the project
  2. It aids in the accurate estimation of activity durations, contributing to effective schedule development and control
  3. It helps in the allocation of project resources
  4. It aids in the formulation of the project budget
B) It aids in the accurate estimation of activity durations, contributing to effective schedule development and control

Data Analysis

In the realm of project schedule management, data analysis techniques hold a pivotal position when it comes to estimating activity durations. The spotlight here falls on two key techniques: alternatives analysis and reserve analysis.

Alternatives analysis allows the project team to weigh resource, cost, and duration variables to determine an optimal approach for accomplishing project work. This analysis can be used to compare various levels of resource capability or skills, scheduling compression techniques, different tools, and make, rent, or buy decisions regarding the resources.

Reserve analysis is another important data analysis technique used in estimating activity durations. It helps determine the amount of contingency and management reserve needed for the project.

Contingency reserves, also known as schedule reserves, are included in duration estimates to account for schedule uncertainty. These reserves are associated with the known-unknowns, which may be estimated to account for potential rework. The contingency reserve may be a percentage of the estimated activity duration or a fixed number of work periods and should be clearly identified in the schedule documentation. As more precise information about the project becomes available, the contingency reserve may be used, reduced, or eliminated.

On the flip side, management reserves serve as a buffer for unforeseen work that remains within the project's scope. These reserves tackle the unknown-unknowns, the unpredictable elements that can throw a project off course. While the management reserve doesn't form part of the schedule baseline, it plays a significant role in shaping the overall project duration requirements. It's worth noting that depending on the contract terms, tapping into management reserves might require a change to the schedule baseline.

What is the primary purpose of alternatives analysis in the Estimate Activity Durations process?
  1. To evaluate identified options to determine the best approach for executing and performing project work
  2. To include contingency reserves in duration estimates to account for schedule uncertainty
  3. To evaluate the cost impact of additional investment in conformance versus the cost of nonconformance
  4. To compare short-term cost reductions with the implication of more frequent problems later in the product life cycle
A) To evaluate identified options to determine the best approach for executing and performing project work

Meetings

In the realm of project schedule management, meetings are more than just a gathering of minds—they are a pivotal mechanism for estimating activity durations. These gatherings offer a fertile ground for the project team to engage in vibrant discussions, dissect tasks, and collectively estimate the time each activity will demand for completion.

In an agile approach, sprint or iteration planning meetings are particularly important. These meetings involve discussing prioritized product backlog items and deciding which items the team will work on in the upcoming iteration. The team breaks down user stories into low-level tasks, estimates the hours required for each task, and validates the estimates based on the team's capacity over the iteration.

Typically, a sprint or iteration planning meeting is held on the first day of the iteration. The attendees usually include the product owner, the Scrum team, and the project manager. These stakeholders bring different perspectives to the meeting, contributing to a more comprehensive and accurate estimation of activity durations.

A well-conducted sprint or iteration planning meeting yields an iteration backlog—a comprehensive list of tasks slated for completion in the forthcoming iteration. But that's not all. The meeting also uncovers assumptions, concerns, risks, dependencies, decisions, and actions tethered to these tasks. These insights serve as a roadmap, guiding the team's efforts during the iteration and helping to keep the project on its scheduled trajectory.

What is the primary purpose of sprint or iteration planning meetings in an agile approach?
  1. To discuss prioritized product backlog items and decide which items the team will work on in the upcoming iteration
  2. To develop a detailed project schedule
  3. To identify and analyze project risks
  4. To provide a detailed cost estimate of the project
A) To discuss prioritized product backlog items and decide which items the team will work on in the upcoming iteration

Bottom-Up Estimating

I recall a time when I was managing a large-scale event planning project. The project was complex, with numerous activities that needed to be scheduled and coordinated. It was during this project that I first utilized the technique of bottom-up estimating in project schedule management.

Bottom-up estimating, as I discovered, is a method that involves dissecting the project into smaller, more manageable components, as defined by the Work Breakdown Structure (WBS). Each component is then estimated individually. It was like putting together a jigsaw puzzle, each piece representing a different part of the project, each with its own time and cost estimate.

When the duration of an activity cannot be confidently estimated, the work within the activity is decomposed into more detail. This process allows for more accurate and reliable estimates, as it is easier to estimate the duration of smaller tasks than larger ones.

Once the detailed durations are estimated, these estimates are aggregated to form a total quantity for each of the activity's durations. This process ensures that all aspects of the activity are accounted for in the total estimate.

Activities within a project may have dependencies between them that can influence the application and use of resources. For example, one activity may need to be completed before another can begin, or two activities may need to be carried out simultaneously. These dependencies can affect the duration and cost estimates of the activities involved.

When dependencies exist among activities, this pattern of resource usage is reflected and documented in the estimated requirements of the activity. This documentation helps to ensure that the dependencies are taken into account in the project schedule and that resources are allocated appropriately.

Reflecting on my event planning project, the use of bottom-up estimating was instrumental in creating a comprehensive and accurate project schedule. It allowed us to account for all the intricate details and dependencies, ensuring that resources were allocated appropriately. This experience underscored the value of bottom-up estimating in project schedule management, a lesson I carry with me in all my subsequent projects.

What is the primary purpose of bottom-up estimating in project schedule management?
  1. To estimate project duration or cost by adding up the estimates of the lower level components of the Work Breakdown Structure (WBS)
  2. To identify the dependencies between project activities
  3. To document the pattern of resource usage in a project
  4. To provide a detailed cost estimate of the project
A) To estimate project duration or cost by adding up the estimates of the lower level components of the Work Breakdown Structure (WBS)