PERT charts have advantages, but managers need to be aware of disadvantages in weighing their use. The Critical Path Method in project management is a step-by-step technique used in the planning process that explains the critical and non-critical activities of a project.
PERT charts depend on the ability to predict precise time frames for multitudes of tasks. Complicated projects involving many activities and suppliers can make this prediction difficult, as explained by U.S. Unexpected events occur, and sometimes the original estimate of time needed for specific steps was inaccurate.
What Is a PERT Chart?
The Program Evaluation Review Technique (PERT) breaks down the individual tasks of a project for analysis. PERT charts are considered preferable to Gantt charts because they identify task dependencies, but they’re often more difficult to interpret. Developed in the late 1950s, Critical Path Method or CPM is an algorithm used for planning, scheduling, coordination and control of activities in a project. Here, it is assumed that the activity duration is fixed and certain. CPM is used to compute the earliest and latest possible start time for each activity.
Content: PERT Vs CPM
Dotted activity lines represent dummy activities—items that are located on another PERT path. Numbers and time allotments are assigned and shown inside each vector. A PERT chart is a project management tool that provides a graphical representation of a project’s timeline.
Cost estimates are developed for each activity in the network. The charts specify the time required to complete each project activity and the activities that must be completed to meet the project completion date. Due to the critical nature of some project objectives, a small business implements controls to make sure projects are successfully completed. One such control mechanism is the Program Evaluation and Review Technique, a program network analysis method used to plan and control large projects, including performance improvement efforts. A project manager arranges the activities of a new project — one without historic precedent — in a diagram, or program network, estimating the time and resources needed to complete each project activity.
Created by Henry Gantt during WWI, Gantt charts are used to visualize a project’s schedule from start to finish. Similar to a PERT chart, Gantt charts display tasks over time to ensure the project is completed on time. The PERT method is a time network analysis that determines labor, material and capital equipment requirements for individual project activities.
The critical path method (CPM), or critical path analysis (CPA), is an algorithm for scheduling a set of project activities. It is commonly used in conjunction with the program evaluation and review technique (PERT). A critical path is determined by identifying the longest stretch of dependent activities and measuring the time required to complete them from start to finish. Program Evaluation and Review Technique (PERT) is a method used to examine the tasked that are in a schedule and determine a variation of the Critical Path Method (CPM). It analyzes the time required to complete each task and its associated dependencies to determine the minimum time to complete a project.
Originally, the critical path method considered only logical dependencies between terminal elements. A related concept is called the critical chain, which attempts to protect activity and project durations from unforeseen delays due to resource constraints.
Key Differences Between PERT and CPM
In project management, a critical path is the sequence of project network activities which add up to the longest overall duration, regardless if that longest duration has float or not. This determines the shortest time possible to complete the project. There can be ‘total float’ (unused time) within the critical path.
- There can be ‘total float’ (unused time) within the critical path.
- This determines the shortest time possible to complete the project.
- In project management, a critical path is the sequence of project network activities which add up to the longest overall duration, regardless if that longest duration has float or not.
A PERT chart is a visual representation of a series of events that must occur within a project’s lifetime. The direction of arrows indicates the flow and sequence of events required for project completion.
An additional parallel path through the network with the total durations shorter than the critical path is called a sub-critical or non-critical path. Activities on sub-critical paths have no drag, as they are not extending the project’s duration. Any project with interdependent activities can apply this method of mathematical analysis. The first time CPM was used for major skyscraper development was in 1966 while constructing the former World Trade Center Twin Towers in New York City.
Programs or Project Management and Review Technique (PERT) is apt for those projects where the time required to accomplish different activities are not known. CPM or Critical Path Method is appropriate for the projects which are reappearing (recurring) in nature. In addition, the method can easily incorporate the concepts of stochastic predictions, using the PERT and event chain methodology.
It estimates the shortest possible time each activity will take, the most likely length of time, and the longest time that might be taken if the activity takes longer than expected. The method was developed by the US Navy in 1957 on the Polaris nuclear submarine project. A good critical path schedule can help to identify the activities that must be completed on time in order to complete the whole project on time.
A Real World Example of a PERT Chart
What do you mean by PERT?
PERT is a project management planning tool used to calculate the amount of time it will take to realistically finish a project. PERT stands for Program Evaluation Review Technique. PERT is similar to critical path in that they are both used to visualize the timeline and the work that must be done for a project.
This might insert dead time (total float) into the schedule on the activities on that path prior to the sunrise due to needing to wait for this event. This path, with the constraint-generated total float would actually make the path longer, with total float being part of the shortest possible duration for the overall project. In other words, individual tasks on the critical path prior to the constraint might be able to be delayed without elongating the critical path; this is the ‘total float’ of that task. However, the time added to the project duration by the constraint is actually critical path drag, the amount by which the project’s duration is extended by each critical path activity and constraint.
Definition of CPM
These questions involve how long it will take to complete an activity, and which other activities must occur immediately before and immediately after this activity for effective project completion. PERT is a good way of making these relationships visible in a diagram. A project can have several, parallel, near critical paths; and some or all of the tasks could have ‘free float’ and/or ‘total float’.
PERT works best in projects where previous experience can be relied on to accurately make these predictions. A PERT chart makes planning large projects easier, according to the University of Pittsburgh School of Information Sciences. It answers three key questions about each activity that help managers identify relationships between tasks and task dependencies.
PERT Chart is acronym for (Program Evaluation and Review Technique). A PERT chart is a project management tool used to schedule, organize, and coordinate tasks within a project. It is basically a method to analyze the tasks involved in completing a given project, especially the time needed to complete each task, and to identify the minimum time needed to complete the total project. A PERT chart, sometimes called a PERT diagram, is a project management tool used to schedule, organize and coordinate tasks within a project. It provides a graphical representation of a project’s timeline that allows project managers to break down each individual task in the project for analysis.
CPM goals are to check time-bound issues and process that causes blockage in the project. The CPM is preferably applicable to projects that involve various activities that are associated in a complex method.