Planning and Scheduling Technique

ABA 2510

COST PLANNING &

CONTROL

LECTURE 5:

PLANNING & SCHEDULING TECHNIQUES

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Introduction

A schedule is the conversion of WBS into an

operating time table, in the form of network of

activity & event relationships that graphically

portrays the sequential relations btn tasks in a

project

Serves as a basis for monitoring & control project activity

A key input in establishing the monitoring & control system

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Benefits of scheduling

Provides a consistent framework for planning,

monitoring & control

Illustrates the interdependency of all tasks,

work packages & elements

Denotes the times when resources must be

available

Determines project completion date

Identifies so called critical activities..

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Benefits of scheduling cont

Identifies activities with float/slack

Identifies dates which tasks must be

started

Identifies which tasks may be run in

parallel

It relieves some interpersonal conflict by

clearly showing task dependencies

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Types of Planning & Scheduling tech

Gantt or bar charts

Milestone charts

Line of balance

Program Evaluation and Review Technique

(PERT)

Arrow Diagram Method (ADM) or

Critical Path Method (CPM)

Graphical Evaluation and Review

Technique (GERT)

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Gantt Chart

Developed around 1917 by Henry L.

Gantt a pioneer in scientific management

Involves the use of bar charts with:

specified start time

completion time and

duration.

Does not show the dependency

relationship among the activities and the

logical flow of the project.

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Gantt Chart cont

Advantages of Gantt charts includes:

Easily understood

Easy to construct

Do not require frequent updating

They provide a picture of the current state of a project

Powerful devices for communicating to senior mgt

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Gantt Chart cont

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Gantt Chart Example

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Network techniques

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Network Techniques

Activity on Arrow

CPM PERT

Activity on Nodes

PNA (PDM)

GERT

Network Fundamentals

Activity is an identifiable, quantifiable, discrete

lowest level element of work, which must be

performed during the course of the project. Each

activity consumes time for their completion.

Example of activities include;

Excavation, Fixing steel, building a wall, constructing a

roof ,curing concrete etc

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Network Fundamentals cont

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Network Fundamentals cont

The activities are represented by arrows pointing

in the forward direction

The tail of the arrow depicts the commencement of an

activity and the arrow head its termination

The length of the arrow is not drawn to scale

Arrows are neither curved nor drawn in reverse

direction

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Event

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It is the state that marks the completion of a

preceding activity & the beginning of a

succeeding one.

It has no duration

Symbolically shown by a circle or ellipse

The events are labeled numerically to identify

them & describe the connecting activities

Event cont

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The first event of a project is called the start event,

and the last, end event

Preceding event- an event at which an activity starts

Succeeding event-the event which terminates an

activity

Key event the event of significance i.e building

ready for occupation, its occurance is termed as a

milestone

Event cont

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Dangling event-The loose events before the addition

of dummies.

Bust & Sink points

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IN fig A, event 26 must take place before event 7,18&

31.In Fig. B event 7,18 & 31 must take place prior to

26.

Sink /Merge

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Dummy activity

It is a superimposed activity, which does not

represent any specific operation or process. it has

Zero duration & consumes no resources. Its

purpose is twofold:

To provide a logical link to maintain the correct

relationship of activities

To simplify the description of concurrent activities in

terms of event numbers

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Dummy activity cont

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F follows C and E starts after completion of C

& D. Activity H provides the logical link

Event timings & Associated terms

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a) Earliest event time(EET)- it is the earliest time an

event can take place, assuming that all the events

prior to it also occur at their earliest time

The EET is set at Zero, while the EET of subsequent

events is calculated by adding the activity duration into it

in the process known as forward pass.

If there is more than one activity terminating into the

event, consider the largest value

Event timings & Associated terms

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b) Latest Event Time (LET)- it is the latest time by

which an event can occur, if the project is to be

completed within the specified time.

Unless otherwise specified, the LET of the end event

EET. The remaining events are calculated by subtraction

in the reverse direction in the process known as

backward pass.

If there is more than one activity diverging from an

event, consider the lowest value

Event timings & Associated terms

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c) Slack- the difference between the LET & EET of an

event

d) Critical events- the events having Zero slack, they

must take place at a stipulated time without fail.

Any change in their occurrence would affect the

project completion time.

Activity timings & Connected terms

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a) Earliest start time(EST)- the earliest time an activity

can be started, assuming that all the activities prior

to it have taken place as early as possible. The EST

of an activity EET of the preceding event

b) Latest start time(LST)the latest time an activity can

start consistent with the completion of the

project in the stipulated time. Determined by

subtracting preceding event

Activity timings & Connected terms

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c) Earliest finish time(EFT)- the earliest time by which

an activity can be completed, assuming that all the

activities prior to it begin at their ESTs

d) Latest finish time(LFT) the latest time by which an

activity must be completed to ensure the

completion of the project within the stipulated

time. LFT=LET

Activity timings & Connected terms

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e) Float/activity slack - the difference between the

latest start time(LST) & the earliest start

time(EST) of an activity

f) Critical activities - the activities including dummy

ones having Zero float

g) Network Critical Path the path of critical

activities (including dummy activities) which links

the start & end events

Duration Estimation Methods

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a) One-time estimate

b) Three-time PERT estimate

c) Non-linear distribution

One-time estimate

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a) Estimation is based on one or more of the

following;

i. Planning data

ii. Past experience on execution of similar project

iii. Average time assessed by experts

Three-times PERT estimate

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When the exact duration of an activity like R &D,

is not certain, duration is computed using;

Where;

Te =Expected completion time

To=Optimistic time, assuming that everything goes extremely well

Tp = pessimistic time, assuming that everything goes wrong

Pm = most likely time, assuming normal conditions

Example

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Questions?

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