Appendix B: Graphical Planning, Scheduling, and Control Tools
Sequencing with Flow Charts
Scheduling with Gantt Charts
PERT Networks
History of PERT.
PERT Terminology
PERT in Action.
Positive and Negative Aspects of PERT.
Terms to Understand
Endnotes
Three graphical tools for planning, scheduling, and controlling operations and projects are flow charts, Gantt charts, and PERT networks. They can be found in project management software programs such as Microsoft Project for Windows.

Sequencing with Flow Charts
Flow charts have been used extensively by computer programmers to identify task components and by TQM (total quality management) teams to simplify work (eliminate wasted steps and activities). Beyond that, flow charts are a useful sequencing tool with broad application. Sequencing is simply arranging events in the order of their actual or desired occurrence. For instance, this book had to be purchased before it could be read. Thus, the event “purchase book” would come before the event “read book” in flow-chart sequence.

A sample flow chart is given in Figure B.1. Notice that the chart consists of boxes and diamonds in addition to the start and stop ovals. Each box contains a major event, and each diamond contains a yes-or-no decision.

Figure B.1  A Sample Flow Chart

Managers at all levels and in all specialized areas can identify and properly sequence important events and decisions with flow charts of this kind. User-friendly computer programs make flow-charting fun and easy today. Flow charts force people to consider all relevant links in a particular endeavor as well as their proper sequence. This is an advantage because it encourages analytical thinking. But flow charts have two disadvantages. First, they do not indicate the time dimension, that is, the varying amounts of time required to complete each step and make each decision. Second, flow charts are not practical for complex endeavors in which several activities take place at once.

Scheduling with Gantt Charts
Scheduling is an important part of effective planning. When later steps depend on the successful completion of earlier steps, schedules help managers determine when and where resources are needed. Without schedules, inefficiency creeps in as equipment and people stand idle. Also, like any type of plan or budget, schedules provide management with a measuring stick for corrective action. Gantt charts, named for Henry L. Gantt, who developed the technique, are a convenient scheduling tool for managers.1 Gantt worked with Frederick W. Taylor at Midvale Steel beginning in 1887 and, as discussed in Appendix A, helped refine the practice of scientific management. A Gantt chart Gantt chart
graphic scheduling technique

 is a graphic scheduling technique that has historically been used in production operations. Things have changed since Gantt’s time, and so have Gantt chart applications. Updated versions like the one in Figure B.2 are widely used today for planning and scheduling all sorts of organizational activities. They are especially useful for large projects such as moving into a new building or installing a new computer network.2

Figure B.2 also shows how a Gantt chart can be used for more than just scheduling the important steps of a job. By filling in the timelines of completed activities, actual progress can be assessed at a glance. Like flow charts, Gantt charts force managers to be analytical as they reduce jobs or projects to separate steps. Moreover, Gantt charts improve on flow charts by allowing the planner to specify the time to be spent on each activity. A disadvantage that Gantt charts share with flow charts is that overly complex endeavors are cumbersome to chart.

Figure B.2  A Sample Gantt Chart

PERT Networks
The more complex the project is, the greater is the need for reliable sequencing and scheduling of key activities. Simultaneous sequencing and scheduling amounts to programming. One of the most widely recognized programming tools managers use is a technique referred to simply as PERT. An acronym for Program Evaluation and Review Technique, PERT PERT (Program Evaluation and Review Technique)
graphic sequencing and scheduling tool for complex projects

 is a graphic sequencing and scheduling tool for large, complex, and nonroutine projects.

History of PERT.
PERT was developed in 1958 by a team of management consultants for the U.S. Navy Special Projects Office. At the time, the navy was faced with the seemingly insurmountable task of building a weapon system that could fire a missile from the deck of a submerged submarine. PERT not only contributed to the development of the Polaris submarine project but was also credited with helping to bring the system to combat readiness nearly two years ahead of schedule. News of this dramatic administrative feat caught the attention of managers around the world. But, as one user of PERT reflected, “No management technique has ever caused so much enthusiasm, controversy, and disappointment as PERT.”3 Realizing that PERT is not a panacea, but rather a specialized planning and control tool that can be appropriately or inappropriately applied, helps managers accept it at face value.4

PERT Terminology
Because PERT has its own special language, four key terms must be understood.

PERT in Action.
A simple PERT network is shown in Figure B.3. The task in this example, the design and construction of three dozen customized golf carts for use by physically challenged adults, is relatively simple for instructional purposes. PERT networks are usually reserved for more complex projects with hundreds or even thousands of activities. PERT events are coded by circled letters, and PERT activities, shown by the arrows connecting the PERT events, are coded by number. A PERT time (T) has been calculated and recorded for each PERT activity.

Figure B.3  A Sample PERT Network

See if you can pick out the critical path in the PERT network in Figure B.3. By calculating which path will take the most time from beginning to end, you will see that the critical path turns out to be A-B-C-F-G-H-I. This particular chain of activities and events will require an estimated 21.75 workdays to complete. The overall duration of the project is dictated by the critical path, and a delay in any of the activities along this critical path will delay the entire project.

Positive and Negative Aspects of PERT.
During the nearly 50 years that PERT has been used in a wide variety of settings, both its positive and negative aspects have become apparent.

On the plus side, PERT is an excellent scheduling tool for large, nonroutine projects, ranging from constructing an electricity generation station to launching a space vehicle. PERT is a helpful planning aid because it forces managers to envision projects in their entirety. It also gives them a tool for predicting resource needs, potential problem areas, and the impact of delays on project completion. If an activity runs over or under its estimated time, the ripple effect of lost or gained time on downstream activities can be calculated. PERT also gives managers an opportunity, through the calculation of optimistic and pessimistic times, to factor in realistic uncertainties about planning horizons.

On the minus side, PERT is an inappropriate tool for repetitive assembly-line operations in which scheduling is dictated by the pace of machines. PERT also shares with other planning and decision-making aids the disadvantage of being only as good as its underlying assumptions. False assumptions about activities and events and miscalculations of PERT times can render PERT ineffective. Despite the objective impression of numerical calculations, PERT times are derived rather subjectively. Moreover, PERT’s critics say it is too time-consuming: a complex PERT network prepared by hand may be obsolete by the time it is completed, and frequent updates can tie PERT in knots. Project management software with computerized PERT routines is essential for complex projects because it can greatly speed the graphic plotting process and updating of time estimates.

Terms to Understand
Gantt chart graphic scheduling technique

PERT (Program Evaluation and Review Technique) graphic sequencing and scheduling tool for complex projects

PERT event performance milestone; start or finish of an activity

PERT activity work in process

PERT times weighted time estimates for completion of PERT activities

Critical path most time-consuming route through a PERT network

Endnotes
1. For examples of early Gantt charts, see H. L.Gantt, Organizing for Work (New York: Harcourt, Brace and Howe, 1919), chapter 8.

2. Gantt chart applications can be found in TomConkright, “So You’re Going to Manage a Project,” Training, 35 (January 1998): 62–67; and AndrewRaskin, “Task Masters,” Inc. Tech 1999, no. 1 (1999): 62–72.

3. IvarsAvots, “The Management Side of PERT,” California Management Review, 4 (winter 1962): 16–27.

4. Additional information on PERT can be found in NancyMadlin, “Streamlining the PERT Chart,” Management Review, 75 (September 1986): 67–68; Eric C.Silverberg, “Predicting Project Completion,” Research Technology Review, 34 (May–June 1991): 46–49; Robert L.Armacost and Rohne L.Jauernig, “Planning and Managing a Major Recruiting Project,” Public Personnel Management, 20 (summer 1991): 115–126; T. M.Williams, “Practical Use of Distributions in Network Analysis,” Journal of the Operational Research Society, 43 (March 1992): 265–270; and HooshangKuklan, “Effective Project Management: An Expanded Network Approach,” Journal of Systems Management, 44 (March 1993): 12–16.

5. Adapted in part from JohnFertakis and JohnMoss, “An Introduction to PERT and PERT/Cost Systems,” Managerial Planning, 19 (January–February 1971): 24–31.