Critical Path Method or CPM was created in the 1950s by James Kelley Jr. and Morgan Walker, according to Peter Stelth and Guy Le Roy of Isles Internationale Université. The tool CPM allows managers to determine what activities within a project deem "critical" and to determine a semi-structured time line of the project. CPM is used for a number of businesses including research, construction and development, according to Grashina Newell, author of "The Project Management Question and Answer Book."
Managers use CPM as a tool to assess and determine time frames for critical projects. The CPM tool identifies specific areas of the project that will take more time than others. Samuel Baker, a student at the University of South Carolina, identifies seven specific steps that occur in CPM. In Step One the manager creates a list of activities including when the activities start and the estimated time length for each activity. Step 2 involves drawing out a diagram that pinpoints the order of activities. In Step 3 the manager creates a CPM spreadsheet. A variety of computer software programs are available for this step. Step 4 involves finding all possible paths through the diagram using the computer program Pathfind or by hand. Step 5 involves entering the path information into the spreadsheet created. During Step 6 the manager calculates the path times. Finally in Step 7, the manager identifies the "critical path."
Managers use CPM for a number of benefits the program offers. CPM controls, schedules and monitors projects. Managers can predict dates for all activities and determine what order the activities will occur. According to Team Bridge of St. Norbert College, CPM also evaluates parallel activities, recognizes more than one critical path and displays dependencies. Managers implement the use of CPM to save money over the long run by taking the guesswork out of project paths.
Managers should consider all known disadvantages to any project management tool. Team Bridge of St. Norbert college identifies four specific disadvantages of Critical Path Method. Disadvantages of CPM include difficulty in predicting activity ending times. Scheduling of personnel and resource allocation are not included, and the critical path is not always discovered easily. CPM becomes complicated as the projects grow in size.
CPM Versus PERT
Program Evaluation and Review Technique compares with CPM as a tool for managers to utilize during projects. Team Bridge at St. Norbert College identifies similarities and differences between PERT and CPM. Similarities include process steps and scheduling of activities. Some differences between PERT and CPM include the fact that PERT is probabilistic where as CPM is deterministic, and CPM examines cost and trade-off and PERT does not.