CPM &PERT

According to Schwalbe (2010), “Critical Path Method (Critical Path Analysis) is a network diagramming technique used to predict total project duration”.

The basic purpose of creating a PERT chart is to determine how much time will take to finish the whole project and can identify the earliest possible dates on which we can expect an activity to start or end (Kerzner, 2006). In PERT, user can easily analyze dates with its network diagram.

Optimistic time (a) - Time an activity will take if everything goes as well as possible

Pessimistic time (b) - Time an activity would take assuming very unfavorable conditions

Most Likely time (m) - Most realistic time estimate to complete the activity

(Rehan, 2012)

According to Rehan (2012),

To find the expected activity time (t), the beta distribution weights the estimates as follows

t = (a + 4m + b)/6

To compute the dispersion or variance of activity completion time, we use the following formula

Variance = ( ( b – a ) / 6 )^2

A series of activities that determines the earliest time by which the project can be completed is called the Critical Path of a project. (Schwalbe, 2010)

The differences between PERT and CPM

•  PERT uses three time estimates (optimistic, most likely and pessimistic) to derive an expected time. CPM uses one time estimate that represents the normal time.

•   PERT is probabilistic in nature, based on a beta distribution for each activity time and a normal distribution for expected time duration. This allows us to calculate the “risk” in completing a project. CPM is based on a single time estimate and is deterministic in nature.

•  Both PERT and CPM permit the use of dummy activities in order to develop the logic.

•  PERT is used for R&D projects where the risks in calculating time durations have a high variability. CPM is used for construction projects that are resource dependent and based on accurate time estimates.

(Kerzner, 2006)

WBS

WORK BREAKDOWN STRUCTURE

Project Management Body Of Knowledge	Information Technology Project Management Kathy Schwalbe	Project Management Harold Kerzner
Create WBS is the process of subdividing project deliverables and project work into smaller, more manageable Components. The work breakdown structure (WBS) is a deliverable-oriented hierarchical decomposition of the work to be executed by the project team to accomplish the project objectives and create the required deliverables, with each descending level of the WBS representing an increasingly detailed definition of the Project work.	Work Breakdown Structure is a deliverable-oriented grouping of the work involved in a project that defines the total scope of the project. Because most projects involve many people and many different deliverables, it is important to organize and divide the work into logical parts based on how will be performed.WBS provides the basis for planning and managing project schedules, costs, resources and changes.	A WBS is a product oriented family tree subdivision of the hardware, services and data required to produce the end product. The WBS is structured in accordance with the way the work will be performed and reflects the way in which project costs and data will be summarized and eventually reported. Preparation of the WBS also considers other areas that require structured data, such as scheduling, configuration management, and contract funding and technical performance parameters. It is the single most elements because it provides a common framework of the project tasks.

When creating a WBS, mainly project deliverables and project work is subdividing into smaller and more manageable components. WBS bestows a hierarchical over-view of a project workflow, it is mentioned in Project Management Body of Knowledge (2008), “The WBS is a deliverable-oriented hierarchical decomposition of the work to be executed by the project team to accomplish the project objectives and create the required deliverables with each descending levels of the WBS representing an increasingly detailed definition of the project work.”

When comparing the WBS definitions in each book, it gives an idea about the WBS. But Kathy Schwalbe and Harold Kerzner has taken the main idea from the Project Management Body of Knowledge. So in Project Management Body of Knowledge definition’s extended definitions are included in other 2 books.

Advantages and disadvantages in using a WBS

Advantages in using a WBS

1.      The WBS reflects the project objectives, by listing all the activities required to accomplish these objectives, it prevents confusion and doubts as to the aim of the project.

2.      It creates a common database and dictionary of common notation that serves as a reference point for all involved parties.

3.      The WBS enables smooth communications among the project team members and between them and customers, suppliers, regulators and etc.

4.      It serves as an archive that can later facilitate knowledge transfer to other projects or learning by new members of the work force.

5.      The WBS is an effective tool for resource management.

(Salvendy, 2001)

Disadvantages in using a WBS

1.      The WBS requires a significant amount of effort to build and maintain.

2.      The WBS encourages rigid structure for the project. Thus it reduces managerial flexibility to initiate and lead changes during the project life cycle.

(Salvendy, 2001)

REFERENCE & BIBLIOGRAPHY

Salvendy, G. 2001, Handbook of Industrial Engineering, 3^rd ed, John Wiley & Sons, Inc, Canada.