Page 286 - The Handbook for Quality Management a Complete Guide to Operational Excellence

272 C o n t i n u o u s I m p r o v e m e n t D e f i n e S t a g e 273

chart shows the units of time (days, weeks, months, etc.). The vertical axis
shows the activ ities to be completed. Bars show the estimated start time
and duration of the various activities.
Modern Gantt charts usually include designation of milestones (events
that take zero time), as well as the individual responsible for each task.
The completed chart clearly shows the task dependencies (i.e., which
activities must be completed before any given activity may be started),
and is often labeled with the critical path. (Historically, CPM [Critical Path
Method] was considered an alternative to Gantt. Similarly, PERT [Program
Evaluation and Review Technique] was developed to evaluate scheduling
based on probabilistic activity times. Today, PERT, CPM, and Gantt actu­
ally comprise one technique.)
Project scheduling consists of four basic phases: planning, scheduling,
improvement, and controlling. The planning phase involves breaking the
project into distinct activities. The time estimates for these activities are
then determined and a network (or arrow) diagram is constructed, with
each activity being represented by an arrow.
The ultimate objective of the scheduling phase is to construct a time
chart showing the start and finish times for each activity as well as its
relationship to other activities in the project. The schedule must identify
activities that are “critical” in the sense that they must be completed on
time to keep the project on schedule.
It is vital not to merely accept the schedule as a given. The information
obtained in preparing the schedule can be used to improve the project
schedule. Activities that the analysis indicates to be critical are candidates
for improvement. Pareto analysis can be used to identify those critical ele­
ments that are most likely to lead to significant improvement in overall proj­
ect completion time. Cost data can be used to supplement the time data, and
the combined time/cost information can be analyzed using Pareto analysis.
The final phase in project management is project control. This includes
the use of the network diagram and time chart for making periodic prog­
ress assessments.
Constructing Network Charts
A common means of evaluating a project schedule is to graphically por­
tray the interrelationships among the elements of a project. This network
representation of the project plan shows all the precedence relationships,
that is, the order in which the tasks must be completed. Arrows in the
network chart represent activities, while boxes or circles represent events;
in preparing and understanding this technique, it is very important to
keep these two terms distinct. An arrow goes from one event to another
only if the first event is the immediate predecessor of the second. If more
than one activity must be completed before an event can occur, then there
will be several arrows entering the box corresponding to that event. Some­
times one event must wait for another event, but no activity intervenes

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