What is Project Decomposition in Six Sigma? Phases, Challenges

  • Post last modified:18 March 2023
  • Reading time:13 mins read
  • Post category:Lean Six Sigma
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What is Project Decomposition in Six Sigma?

In Six Sigma, project decomposition is the process of breaking down a complex project into smaller, more manageable tasks and sub-projects that can be easily tracked and monitored. This is an important step in the Define, Measure, Analyze, Improve, Control (DMAIC) methodology used in Six Sigma projects, as it helps to ensure that the project stays on track and meets its goals.

Project decomposition involves identifying all of the tasks required to complete the project and organizing them into a logical sequence. This typically involves creating a work breakdown structure (WBS), which is a hierarchical list of all the tasks required to complete the project.

Whenever there is a large and complex project at hand, it is advisable to break the project into smaller projects which can be further broken down into work activities and tasks. This type of breaking down of bigger work into smaller and manageable components is called decomposition.

Decomposition is a process of moving from project objectives to tasks. The decomposition of a project also results in a clear description of the project scope. Project decomposition entails a chronological breakdown of the project work into smaller components.

This breakdown is done based on the function and role performed by each element in the project. One of the main objectives of decomposition is to classify different work items and create a bigger view of the project management process.

During decomposition, key elements/activities/work of the project are planned by creating an activity-based hierarchy. There can be multiple levels in such a hierarchy. The resulting hierarchy is called Work Breakdown Structure (WBS). WBS is a preferred method of project decomposition. It can be used in a majority of projects but it finds special use in engineering and construction projects which are traditionally known to have an activity-based hierarchy of work. The project starts with phases and activities and is broken down into tasks and activities.

Phases are broken down into activities which are broken down into milestones. Finally, milestones are broken down into tasks. Thus, phases, activities, milestones, and tasks are the major elements of the project management process. The project team must manage these four things throughout the project.

WBS Approach in Project Decomposition

WBS is the most preferred method of project decomposition. However, there are many other options as well. One of the easiest ways to decompose a project is the visual display of different steps starting from the largest to the smallest. This approach is known as the top-down approach. The top-down approach to decompose a project is applied using the following steps:

Step One: Identification of Project Deliverables

Before starting the process of project decomposition, the project team must identify the project deliverables or milestones. The entire project is broken down into smaller works or tasks called work packages, and each task is broken down into deliverables.

Step Two: Handle One Deliverable at a Time

Traditionally, the decomposition exercise during the initial stage of the project is done with the use of pencil and paper (manually). Experts believe that the traditional method of using pencil and paper creates the least amount of frustration. Using a separate piece of paper for each deliverable is the best and least confusing method. The individual paper offers ample space for making a rough draft. Each paper should be designated with the deliverable name.

Step Three: Dealing With Each Deliverable Individually

Managers can avoid confusion by dealing individually with every deliverable. The process would involve selecting the first deliverable and keeping the piece of paper in front. The first question that is asked at this stage is: “What would be the first step required to achieve the deliverable?” For example, if you were to throw a lunch party at your home, deliverables would include the identification of guests, sending invitations to them, and serving food to all the guests.

Step Four: Know Your Stop Point

Project activities may go on and on. A project deliverable can be considered to be broken down sufficiently when the expected duration and cost can be accurately determined, and everyone has clarity on what needs to be done exactly in every step. This process can be repeated for all deliverables till the time all the deliverables have been decomposed to the extent that one can sufficiently estimate the duration and cost.

Step Five: Duration Estimation and Work Packaging

Once the deliverables are broken down using paper and pen, the paper would appear like a filled-up box. After this, these boxes need to be organized into work packages that essentially contain action items that are related in some way and that will be assigned to resources for completion. Estimation of the amount of time that will be required by every task needs to be carried out before this activity.

After this, all tasks can be grouped as per the resource requirement. According to Joseph Phillips, author of PMP Project Management Professional Study Guide, a package should be neither less than work worth eight hours nor more than work worth eighty hours.

Step Six: Estimate Task Costs

Lastly, the cost of each task needs to be estimated. Once this is done, the project manager can accurately estimate the project budget. This step holds its importance because certain tasks have costs that are dependent on time while others may have some resource requirements that have attached costs. Once the task estimation exercise is complete, decomposed deliverables can be arranged in the WBS.

WBS makes it easy for a Six Sigma leader to visualize tasks with granularity. The advantages of project decomposition and identified work packages are:

  • Accurate time and cost estimates
  • Clarity of the scope
  • Effective risk identification and containment
  • Improved control during project execution
  • Efficient and accurate planning
  • Accurate visualization of the impact of any change in scope
  • Cost estimates are used for reference in future projects
  • Functions as a useful reference tool for WBS for future projects

Challenges of Project Decomposition in Six Sigma

Even though decomposition is beneficial for a project, there are some challenges and disadvantages of project decomposition as well. These are discussed as follows:

Getting Too Microscopic Details

There is no doubt that detailing helps managers bring efficiency to the project. However, there is a flip side to going overboard about this. Deeper details than what is required do not offer any additional benefits; instead, they may lead to a waste of time and resources. Hence, it is important to determine the right amount of details that need to be included. Some questions that managers can ask to determine the degree of decomposition include:

  • Is the quantity of work packages small enough for the team to be able to determine cost, time, and schedule?
  • Are project leaders and teams satisfied with the amount of detailing available?
  • Is assigning a resource to a small work package possible?

Assurance of Team’s Comfort Level

WBS is an activity that cannot be carried out without the involvement of the team. Managers need to have strong facilitation skills to ensure maximum participation from team members and that they remained focused. Discomfort among team members related to sharing of ideas may sometimes lead to a loss of important information.

Considering Wbs as a Schedule

WBS functions as an important tool because it is a source of detailed information that meets project goals and objectives. WBS should not be seen as a plan or schedule. It is a visual representation of the project and can be shared with stakeholders for the same purpose. Investing time in creating WBS decreases the possibility of missing work components during project execution.

Article Source
  • Ferraro, J. (2012). Project management for non-project managers. New York: AMACOM.

  • Jeff Furman. (2015). The Project Management Answer Book; 2nd Edition. Management Concepts, Inc.

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