From Gantt Charts to Planning Poker

From Gantt Charts to Planning Poker

A Comparative Dive into PERT and Agile Story Points Estimation

When estimating, it's crucial to consider the contractual relationship between the engineering team and the project sponsor. Whether it's a retainer, fixed fee, or time and materials (T&M) contract, understanding the contract type is fundamental as it dictates the nature of estimates. A retainer contract typically focuses on reserving personnel, while a fixed fee contract specifically purchases deliverables. However, beyond contracts, examining our chosen project management framework is essential. This comparison involves understanding the differences in estimating between Agile and Traditional methodologies when determining our approach to estimation.

Two distinct methodologies stand out: Traditional Program Evaluation and Review Technique (PERT) and Agile Story-point Estimating. While PERT has long been heralded for its structured approach to project planning and scheduling, Agile Story-point Estimating has emerged as a flexible and collaborative alternative, particularly suited to the iterative nature of Agile development. In this article, we embark on a comparative journey, exploring the key differences and similarities between these two approaches. By understanding the strengths and weaknesses of each methodology, project managers can make informed decisions to effectively plan and execute projects in diverse environments.

Introduction to PERT

The Program Evaluation and Review Technique (PERT) is a project management method used to estimate the time required to complete a project. PERT was developed in the late 1950s by the U.S. Navy for the Polaris missile project. It involves breaking down the project into smaller tasks and estimating the time required for each task. PERT utilizes a network diagram to visualize task dependencies and the critical path, which is the longest sequence of dependent tasks determining the minimum time needed to complete the project.

Introduction to Story-points

Story point estimating is a technique used in Agile project management methodologies, particularly in Scrum, to estimate the relative effort required to implement user stories or tasks within a sprint. Unlike traditional time-based estimates, story points represent the effort required, considering factors such as complexity, uncertainty, and risk.

Applying PERT

PERT has several strengths, including its ability to handle uncertainty and variability in task durations by using three time estimates: optimistic, most likely, and pessimistic. This makes PERT suitable for complex projects with many unknowns. Additionally, PERT provides a visual representation of project tasks and their dependencies, allowing project managers to identify critical tasks and allocate resources effectively. However, PERT relies heavily on estimates, which can be subjective and prone to bias. It may also require significant time and effort to create and maintain the network diagram, especially for large projects.

An evaluation framework can help determine when PERT is most appropriate for a project. PERT is well-suited for projects with high uncertainty and complexity, where traditional estimating methods may not be sufficient. Additionally, PERT is beneficial when stakeholders require a probabilistic estimate of project duration rather than a single-point estimate. However, PERT may not be suitable for projects with well-defined tasks and known durations, as the additional complexity of PERT may not provide significant value compared to simpler estimation methods.

To create a PERT estimate for a project, follow these steps:

  1. Identify all tasks required to complete the project.
  2. Break down each task into smaller, more manageable subtasks if necessary.
  3. Determine the optimistic (O), most likely (M), and pessimistic (P) time estimates for each task.
  4. Calculate the expected duration (TE) for each task using the formula: TE = (O + 4M + P) / 6.
  5. Create a network diagram illustrating task dependencies and the critical path.
  6. Identify the critical path, which consists of the longest sequence of tasks determining the minimum project duration.
  7. Estimate the total project duration by summing the expected durations of tasks along the critical path.
  8. Review and adjust estimates as needed based on expert judgment and historical data.

PERT is a valuable tool for estimating project durations, particularly in situations with high uncertainty and complexity. Its strengths lie in its ability to handle variability and visualize project tasks and dependencies. However, PERT may not be suitable for all projects, particularly those with well-defined tasks and known durations. By evaluating project characteristics and following a structured approach to creating PERT estimates, project managers can effectively utilize PERT to plan and manage projects.

Applying Story-points

Story point estimating offers several advantages. Firstly, it encourages collaboration among team members during estimation sessions, fostering a shared understanding of the work. It also allows teams to focus on relative sizing rather than absolute time, which can be more accurate and less prone to bias. Additionally, story points accommodate uncertainty and changes inherent in Agile projects, providing flexibility in planning and prioritization. However, story point estimating may require initial calibration and ongoing refinement to ensure consistency and accuracy across the team. It may also be challenging for stakeholders accustomed to time-based estimates to understand and compare.

To determine when story point estimating is appropriate, consider the nature of the project and the team's familiarity with Agile practices. Story point estimating is well-suited for Agile projects characterized by evolving requirements, frequent changes, and a collaborative team environment. It is particularly effective for teams with a high degree of domain knowledge and experience in Agile development. However, story point estimating may not be suitable for projects with strict deadlines or fixed scope, where traditional time-based estimates may be more appropriate.

Here's a step-by-step guide for implementing story point estimating in an Agile framework:

  1. Define the unit of estimation (e.g., user stories, tasks) and establish a common understanding of what constitutes a story point.
  2. As a team, select a reference story or task of moderate complexity and assign it a baseline story point value (e.g., 1, 2, 3, 5, 8).
  3. During estimation sessions, compare new stories or tasks to the reference story, considering factors such as complexity, effort, risk, and dependencies.
  4. Discuss and debate the relative size of each story or task compared to the reference, using techniques like Planning Poker or Fist of Five to achieve consensus.
  5. Assign story points to each story or task, aiming for relative sizing rather than absolute accuracy.
  6. Regularly review and refine the team's estimation process based on feedback and historical data, adjusting story point scales and practices as needed.

Story point estimating is a valuable technique in Agile project management, providing teams with a flexible and collaborative approach to estimating effort. Its strengths lie in its ability to accommodate uncertainty, promote team collaboration, and support iterative planning and prioritization. However, story point estimating may require calibration and ongoing refinement to ensure accuracy and consistency. By evaluating project characteristics and leveraging Agile principles, teams can effectively utilize story point estimating to plan and deliver successful projects.

Conclusion

In the realm of project management, the choice between Traditional PERT and Agile Story-point Estimating is not one of superiority but rather one of alignment with project goals, team dynamics, and organizational culture. While PERT excels in providing a structured framework for deterministic planning, Agile Story-point Estimating offers adaptability and responsiveness to change, crucial elements in today's fast-paced business landscape. By leveraging the strengths of both methodologies or selecting the most appropriate approach based on project characteristics, project managers can navigate complexities with confidence, ultimately driving success and delivering value to stakeholders.

Njoki (Wairua) G.

Healthcare Management Leader | AI-Driven Solutions Expert | Speaker | ForbesBLK Member | MBA, PMP?, BSc.

10 个月

Thank you for sharing this insightful comparative analysis between PERT and Agile Story Points Estimation, Alex Feder. Understanding the contractual relationship and project management framework is indeed crucial in guiding estimation processes effectively. Your exploration of these two methodologies provides valuable insights into their respective strengths and weaknesses, helping project managers make informed decisions tailored to their project's needs. Your commitment to highlighting universal principles across industries is commendable and contributes significantly to advancing our profession. Keep up the great work!

Russell Buyse

Product & Technology Executive

11 个月

Nicely explained!

Akash Limbani

Founder & CEO at Cogtix | Microsoft Tech Expert | Innovating AI-driven Software Solutions | Specialist in Custom, Cloud, and Mobile Apps Development | Leading High-Performing Offshore Teams | Empowering Businesses

11 个月

Congratulations on sharing your insights on estimation approaches in software development. Your article provides valuable considerations for project management methodologies.

Vadym Melnyk

Technical Project Manager

11 个月

Thanks for sharing. With a decade in technical program management, I've seen firsthand the importance of matching these methods to project specifics and organizational needs. PERT's structured approach suits projects with high uncertainty, while Agile Story Points excel in environments requiring flexibility and iterative feedback. Choosing between PERT and Agile goes beyond superiority, focusing on alignment with project goals. My experience suggests blending both methods can offer the best of structured planning and adaptability, especially in dynamic projects. Continuous refinement of estimates, based on team feedback and project evolution, is crucial regardless of the method.

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