This article gives you a holistic idea about two popular project management techniques: PERT and CPM. In this article, you will learn about the significance, uses, methodology of the techniques, and role of Gantt Chart in the project management.
- Common Terms
- Pre Project Activity
- Significance of CPM/PERT
- Gantt Charts:
- Brief History of PERT and CPM
- Framework for PERT and CPM
- Drawing the CPM/PERT Network
PERTProgram Evaluation and Review Technique
CPMCritical Path Method Basically, PERT, CPM are the 2 popular project management techniques, which have been created out of the need of Western industrial and military establishments to plan, schedule and control complex projects.
Common TermsTo understand the whole concept of these techniques, we need to know some important terms that are used,
Critical PathThe longest complete path of a project.
Critical TaskA single task along a critical path
DeliverablesSomething of value generated by a team or individual as scheduled often taking the form of a plan, report, procedure, product, or service.
Dependent TaskA task or subtask that cannot be initiated until a predecessor task or several predecessor tasks are finished.
Dummy TaskA link that shows an association or relationship between two otherwise parallel tasks along a PERT/CPM network.
MilestoneA significant event or juncture in the project.
Noncritical TaskA task within a CPM network for which slack time is available.
Parallel TaskTwo or more tasks that can be undertaken at the same time. This does not imply that they have the same starting and ending times.
PathA chronological sequence of tasks, each dependant on the predecessors.
Predecessor TaskTask that must be completed before another task can be completed.
ProjectThe allocation of resources over a specific timeframe and the coordination of interrelated events to accomplish an overall objective while meeting both predictable and unique challenges.
Project ConstraintA critical project element such as money, time, or human resources.
Scope of the project or scope of the projectThe level of activity and effort necessary to complete a project and achieve the desired outcomes as measured by hours, days, resources consumed, and funds spent.
SlackMargin or extra room to accommodate anticipated potential short falls in planning
Slack TimeThe time interval in which you have leeway as to when a particular task needs to be completed.
Task or EventA divisible, definable unit of work related to a project, which may or may not include subtasks.
TimelineThe scheduled start and stop times for a subtask, task, phase or entire project.
Pre Project ActivityBefore attempting to use or know about these tools, the project’s information must be assembled in a certain way. It includes a basic description of the preceding steps.
- Setting the project start date
- Setting the project completion date
- electing the project methodology or project life cycle to be used
- Determining the scope of the project in terms of the phases of the selected project methodology or project life cycle
- Identifying or selecting the project review methods to be used
- Identifying any predetermined interim milestone or other critical dates which must be met.
- Listing tasks, by project phase, in the order in which they might be accomplished.
- Estimating the personnel necessary to accomplish each task
- Estimating the personnel available to accomplish each task
- Determining skill level necessary to perform each task
- Determining task dependencies
- Which tasks can be done in parallel?
- Which tasks require the completion of other tasks before they can start?
- Project control or review points
- Performing project cost estimation and cost-benefit analysis
Significance of CPM/PERTThere are many variations of CPM/PERT which have been useful in planning costs, scheduling manpower and machine time. The main significance of using CPM/PERT is that, they answer the following important questions of a project,
- How long will the entire project take to be completed? What are the risks involved?
- Which are the critical activities or tasks in the project which could delay the entire project if they were not completed on time?
- Is the project on schedule, behind schedule or ahead of schedule?
- If the project has to be finished earlier than planned, what is the best way to do this at the least cost?
Gantt Charts:Henry Gantt who the Gantt chart is named, worked for the department of defense during the First World War. The chart is widely used as a project management tool. The Gantt chart allows you to see start and stop date for project task and subtask. Gantt Charts are derived from your Work Breakdown Structure (WBS)
Work breakdown StructuresThe development of a project plan is predicated on having a clear and detailed understanding of both the tasks involved, the estimated length of time each task will take, the dependencies between those tasks, and the sequence in which those tasks have to be performed. Additionally, resource availability must be determined in order to assign each task or group of tasks to the appropriate worker. One method used to develop the list of tasks is to create what is known as a work breakdown structure. A work breakdown structure (WBS) is a hierarchic decomposition or breakdown of a project or major activity into successive levels, in which each level is a finer breakdown of the preceding one. In final form a WBS is very similar in structure and layout to a document outline. Each item at a specific level of a WBS is numbered consecutively (e.g., 10, 10, 30, 40, 50). Each item at the next level is numbered within the number of its parent item (e.g., 10.1, 10.2, 10.3, 10.4). The WBS may be drawn in a diagrammatic form (if automated tools are available) or in a chart resembling an outline. The WBS begins with a single overall task representing the totality of work to be performed on the project. This becomes the name of the project plan WBS. Using a methodology or system life cycle (analysis, design and implementation) steps as a guide, the project is divided into its major steps. The first phase is project initiation; the second major phase is analysis, followed by design, construction, testing, implementation, and post-implementation follow-up. Each of these phases must be broken in their next level of detail, and each of those, into still finer levels of detail, until a manageable task size is arrived at. The first WBS level for the life cycle would be:
WBS Number Task Description1.0 Project initiation 1.1 Draft project plan 2.0 Analysis phase 2.1 Plan user interviews 2.2 Schedule users interviews 3.0 Examination and test 4.0 Design 5.0 Test 6.0 Implementation Tasks at each successively finer level of detail are numbered to reflect the task from which they were derived. Thus, the first level of tasks would be numbered 1.0, 2.0, 3.0, and so forth. Each of their subtasks would have a two-part number: the first part reflecting the parent task and the second part, the subtasks number itself, such as 1.1, 1.2, or 1.3. As each of these, in turn, decomposed or broken down into its component tasks, each component receives a number comprised of its parent number plus a unique number of its own.
Brief History of PERT and CPMCPM was the discovery of M.R.Walker of E.I.Du Pont de Nemours & Co. and J.E.Kelly of Remington Rand, circa 1957. The computation was designed for the UNIVAC-I computer. The first test was made in 1958, when CPM was applied to the construction of a new chemical plant. Unproductive time was reduced from 125 to 93 hours. PERT was devised in 1958 for the POLARIS missile program by the Program Evaluation Branch of the Special Projects office of the U.S.Navy, helped by the Lockheed Missile Systems division and the Consultant firm of Booz-Allen & Hamilton.
Framework for PERT and CPMEssentially, there are six steps which are common to both the techniques. The procedure is listed below:
- Define the Project and all of its significant activities or tasks. The Project (made up of several tasks) should have only a single start activity and a single finish activity.
- Develop the relationships among the activities. Decide which activities must precede and which must follow others.
- Draw the "Network" connecting all the activities. Each Activity should have unique event numbers. Dummy arrows are used where required to avoid giving the same numbering to two activities.
- Assign time and/or cost estimates to each activity
- Compute the longest time path through the network. This is called the critical path.
- Use the Network to help plan, schedule, monitor and control the project.
- Is this a Start Activity?
- Is this a Finish Activity?
- What Activity Precedes this?
- What Activity Follows this?
- What Activity is Concurrent with this?