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If you’re not using PERT for estimation then you’re missing an opportunity to create the best possible schedule.
Linda’s team had a problem. They faced a mandate to deliver a new product before an inflexible tradeshow deadline. The order to meet this deadline had come from high levels within the company and there was only a slim chance of changing anyone’s mind. How can Linda, as team leader, provide upper management with a fact-based plan to demonstrate either a) what would need to happen to meet this aggressive schedule or b) that the proposed schedule is not achievable?
Linda’s conundrum is about estimation. In our work we see many Product Development teams that struggle over this issue. There are numerous tools for estimating project schedules each of which has its benefits. However, we find that the PERT method, and especially the Network Diagram portion of the process, is the most speedy and effective way to build a realistic, evidence-based schedule.
Creating the PERT Network Diagram helps to improve communication, reduce time to market, and gets your team on the same page. It breaks projects down into tasks, shows the dependencies of one work stream on another, and provides real estimates, created by the people who actually perform the tasks. If you’re not using PERT for estimation then you’re missing an opportunity to create the best possible schedules.
If Linda and her team expect to create a schedule that will meet an aggressive deadline, or show management that the schedule is impossible to achieve, then it’s well worth the couple of hours required to create the Network Diagram portion of the PERT method.
PERT Basics
PERT is a method of analyzing the tasks and time required to complete a complex project. A project’s core team usually creates the diagram, using a range of date estimates for the completion of tasks, to create a probabilistic plan. Teams then use this plan to establish a Critical Path.
PERT charts accommodate any level of complexity. To begin the PERT process, start with major blocks of work. We recommend beginning with a single major milestone. It is important that: 1) the people who are doing the work identify the tasks required to achieve the milestone and 2) that these same subject matter experts estimate how long the tasks will take. Estimate each task using an algorithm: estimate for best case, estimate for worst case, and then provide most probable estimate.
- Gather cross-functional team members and describe the project (ensure you have included all key partners)
- Using Post-it® notes, each team member writes down key tasks (with a 1-2 week granularity for a 6 month project)
- This should result in 18-40 tasks
- For each task, estimate the range in weeks (minimum, typical, maximum) and compute the estimated duration using weighted averages
Then, turn these tasks into a Network Diagram which shows dependencies between tasks. By adding arrows on Post-it’s as required, connect tasks with their predecessors and dependencies. Finally, working through the diagram, identify the critical path – the longest path that ensures all tasks are completed.
Benefits of PERT and the Network Diagram
The Network Diagram is one of the most powerful tools in the PERT methodology because it allows the team to see all of the work required to achieve a milestone. This is vitally important in our functionally-oriented, stovepipe corporate cultures because the diagram causes your team to have to articulate connections between tasks and between functions, facilitating collaboration all across the project. Along the way, we find that the network diagram tends to shift focus to what a customer needs rather than what a functional manger needs.
PERT is effective because…
- It empowers teams to create their own schedule
- It increases predictability by getting all of the functional inputs into key milestones
- It reduces Time to Market by forcing the team to acknowledge what is on the critical path and helps them to reduce its duration
If your group, like Linda’s, is facing a top-down mandate, or an aggressive schedule due to any cause, then your best chance of surviving is to invest a couple of hours in creating the Network Diagram. We have seen many teams that are missing a golden opportunity to create a realistic schedule that is truly predictive and trustworthy. If you are not using it already, it may be time to get this tool into your tool-box.