Operation Management
Project Planning Techniques: CPA, PERT and Gantt Charts

Using appropriate examples discuss project planning techniques. Using clear analysis, apply the planning theories of CPA, PERT and Gantt Charts to a project or projects of your choice.

 

In the context of project or operation management, there are various useful tools that can be used for project planning and control purposes (Gaither et. al., 1999). In this section, three project planning techniques will be discussed. The three project planning techniques are: CPA, PERT and Gantt charts.

 

PERT and CPA

Program Evaluation and Review Technique (PERT) is a planning framework used for planning and tracking of projects’ schedule. Under the PERT framework, the sequence of the tasks are shown and analyzed. The PERT chart however is a graphical representation of the tasks to be performed under a certain project (Krajewski et. al., 2008). It is a tool widely used simultaneously with the concept of Critical Path Analysis (CPA). The critical path is referred to the flows of tasks that must be completed in order to meet the intended completion deadline. Technically, as will be shown in the following examples, the critical path is the path with zero time slack.

The usually, the PERT chart is constructed in a network diagram. The PERT chart in the network diagram is constructed using several attributes, such as earliest and latest start dates for each task, earliest and latest finish dates for each task, and slack time between tasks (Krajewski et. al., 2008).

In the following sections, examples will be given to demonstrate the applications of the PERT and CPA techniques for managing a project. The durations as well as the various activities of the project X are outlined in Table 1. From the information, a network diagram can be constructed, and then, the PERT and CPA methods can be applied to analyze the project.

 

Table 1: Durations and Activities on Project X

 table1

 

In Figure 1, the network diagram is constructed from the information provided in Table 1 above. Such an analysis is necessary to determine the critical path of the projects, and to be performed prior to the applications of the PERT methods.  As shown in Figure 1, the activity on node with critical path is shown in red colored (remark: critical path is the path with zero slack time). From such a diagram, project manager can understand the most critical path in project X that must be paid serious attention on to avoid delay in completion time.

 

Figure 1: Network Diagram for Project X

fig1

 

Conventions used include:

ES: Early Start = earliest time an activity can start

EF: Early Finish = earliest time an activity can finish

LS: Late Start = latest time an activity can start

LF: Late Finish = latest time an activity can finish

 

As demonstrated above, the analysis above is known as the critical path analysis (CPA) method. It can be shown that it is deterministic in nature, whereby a fixed time estimates is computed and used in each of the activities. This makes the CPA method easy to understand. However, the drawback of such a deterministic approach is that it never takes the possible variation in completion time into consideration. When each of the activities in a project has completion times of different probabilities, then the expected fastest possible completion time, on the critical path will be different.

In order to deal with the uncertainty, PERT method can be used. The PERT method is different from the CPA method primarily due to its ability to incorporate uncertainty into the computation of completion times for a project. Generally speaking, three time estimates are used for each and every activity in the project. The three time estimates are: (a) optimistic time, (b) most likely time, and (c) pessimistic time (Gaither et. al., 1999). The meaning of optimistic time is that the best possible and shortest time in which the activity can be completed. It is normal to assume that the optimistic time is three standard deviations from the mean value of the completion time. From another perspective, the most likely time is the completion time with the completion time with the highest probability. On the other hand, the pessimistic time is the longest time that a particular activity may require for completion. Normally, it is assumed that the pessimistic time is three standard deviations from the mean value of the completion time. Under the PEST method, the expected completion time can be calculated from formula below (Stevenson, 2007):

 

Expected Time = (Optimistic Time + 4*Most Likely Time + Pessimistic Time) / 6

 

The expected time will be used instead in each of the node in the network diagram to calculate the completion time expected for a particular project.

 

Gantt Charts

Another useful project planning technique is Gantt Charts. To begin, Gantt Charts are graphical representation of the timing, duration, and the various activities in a project under a chart – designed to demonstrate the sequences of the various activities in a project (Markland et. al., 2001). It is a widely used tool and available in the many project management software packages.

In the following section, an example will be provided on how to apply Gantt Charts to project Y. The durations, activities and details of project Y is shown in Table 2 below.

 

Table 2: Durations and Activities of Project Y

table2

 

From the information provided above, Gantt chart can be generated. The Gantt chart for Project Y is displayed in Figure 2 below. It can be seen that the various activities and the sequences of the activities are displayed clearly in the Gantt chart.

 

Figure 2: Gantt Charts for Project Y

 table-4

 

References

Chase, R. B., Aquilano, N. J., and Jacobs, F. R. (2005). Production and operations management:  manufacturing and services.  Boston, MASS.:  Irwin/McGraw-Hill.

Davis, M. M., Aquilano, N. J., and Chase, R. B. (2000). Fundamentals of operations management. Boston, MASS.: Irwin/ McGraw-Hill.

Gaither, N., and Frazier, G. (1999). Production and operations management.  Cincinnati, OH: South-Western.

Heizer, J. H., and Render, B. (2006). Operations management. Upper Saddle River, N.J.: Prentice Hall.

Krajewski, L. J., and Ritzman, L. P. (2008). Operations management: strategy and analysis. Reading, MASS.: Addison Wesley.

Markland, R. E., Vickery, S. K., and Davis, R. A. (2001). Operations management: concepts in manufacturing and services.  Cincinnati, OH:  South- Western College Pub.

Marks, P. (2010). Are you a project management Gantt chart slave? Project Smart 2000-2010.

Stevenson, W. J. (2007). Production/operations management. Boston, MASS.: Irwin/ McGraw-Hill.

Wilson, J. M. (2003). Gantt charts: a centenary appreciation. European Journal of Operation Research, 149, 430-437.

 

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