PERT is a project management tool used to schedule, organize, estimate and coordinate tasks within a project. PERT stands for Program Evaluation Review Technique, a methodology developed by the U.S. Navy in the 1950s to manage the Polaris submarine missile program
It has two variants
- PERT Chart – used for project scheduling
- PERT estimation also known as three point estimation
Pert Chart
A PERT chart is nothing but graphical depiction of a project. It is similar to a network diagram. It consisting of numbered nodes, in the form of circles or rectangles, representing events, or milestones in the project linked by labelled vectors, directional lines, representing tasks of the project.
The sequence of tasks is defined by direction of the arrows on the lines. Below diagram is showing one example of PERT Chart.
The tasks between nodes 1, 2, 4, 8, and 9 must be completed in sequence. These are called dependent or serial tasks.
The tasks between nodes 1 and 2, and nodes 1 and 3 are not dependent on the completion of one to start the other and can be undertaken simultaneously. These tasks are called parallel or concurrent tasks.
There are tasks which must be completed in sequence but that don’t require resources or completion time are considered to have event dependency. These are represented by dotted lines with arrows and are called dummy activities. For example, the dashed arrow linking nodes 6 and 8.
The numbers on the opposite sides of the vectors indicate the time allotted for the task.
Pert chart is though similar to Gantt chart but sometimes it is preferred over Gantt chart. Reason is the clarity with which it illustrates task dependencies. The disadvantage of PERT chart is it’s much more difficult to interpret especially when we are talking about a complex project where dependencies are many. It also depends on ones ease as Project Manager with the tool.
PERT Estimation
This technique is also referred as Three Point Estimation. This concept originated with the program evaluation and review technique (PERT). PERT uses three estimates to define an approximate range for an activity’s duration:
Most likely (tM). This estimate is based on the duration of the activity, given the resources likely to be assigned, their productivity, realistic expectations of availability for the activity, dependencies on other participants, and interruptions.
Optimistic (tO). The activity duration based on analysis of the best-case scenario for the activity.
Pessimistic (tP). The activity duration based on analysis of the worst-case scenario for the activity.
Depending on the assumed distribution of values within the range of the three estimates the expected duration, tE, can be calculated using a formula. Two commonly used formulas are triangular and beta distributions. The formulas are:
Triangular Distribution. tE = (tO + tM + tP) / 3
Beta Distribution (from the traditional PERT technique). tE = (tO + 4tM + tP) / 6
Duration estimates based on three points with an assumed distribution provide an expected duration and clarify the range of uncertainty around the expected duration.
- What are Scrum roles and why it’s needed? - August 12, 2017
- Stakeholder Analysis – Is it required? - July 28, 2017
- Project Manager – An integrator, how? - July 28, 2017
- Different PMI Certifications – Which one to choose? - July 28, 2017
- What is the importance of Change Management in Project Management? - June 23, 2017
- What’s important to know to build a career in Agile? - June 23, 2017
- Agile Basics, Manifesto & Principles - June 23, 2017
- Scrum – Is it mandatory to learn in today’s IT market? - June 2, 2017