Practical session 1 (critical path analaysis)

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Practical Session Critical Path
Analaysis
Practice 1
Abdisalam Issa-Salwe
Department of Computer Science
Faculty of Information Science and Technology
East Africa University
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Critical Path Analysis (CPA)
 Also known as Critical Network Analysis
 Developed by Dupont and Remington Rand in the
late 1950s for managing plant maintenance
projects
 Uses one duration estimate for each activity
 Provides basic framework for project planning and
control
East Africa University, Faculty of Information Science and Technology, Department of Computer Science

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Critical Path Analysis (cont…)
 Critical Path Analysis (CPA) is a project management tool
that:
 Sets out all the individual activities that make up a larger
project.
 Shows the order in which activities have to be undertaken.
 Shows which activities can only taken place once other
activities have been completed.
 Shows which activities can be undertaken simultaneously,
thereby reducing the overall time taken to complete the
whole project.
 Shows when certain resources will be needed – for
example, a crane to be hired for a building site.
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 A basic understanding of how a project's schedule
is calculated can provide a much clearer
understanding of what should happen when.
 At the heart of Microsoft Project is an algorithm
that uses critical path analysis (CPA) to calculate
a project’s schedule.
 As the tasks within a project have links between
them, they cannot all happen at the same time.

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 Critical path analysis (CPA) is a mathematical
procedure that calculates a project's schedule
 Taking each task in turn it firstly calculates how
quickly the task can be accomplished - its early
start and early finish dates
 Once all these dates have been calculated, the
project finish date can also be determined.
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 Network analysis requires breaking down the
project into task with estimate durations and
establishing a logical sequence.
Enables the minimum possible duration of the
project to be found
Pinpoints the tasks which are on the critical
path,
 i.e. those tasks which, if delayed beyond the
allocated time, would delay the completion of
the project as a whole.

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 Estimate the time needed to complete each
individual activity or task that makes up a part of
the project
 Sort out what activities must be done one after
another, and which can be done at the same time,
if required
 Estimate the critical path: the longest sequence of
consecutive activities through the network.
8 East Africa University, Faculty of Information Science and Technology, Department of Computer Science

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Activity on Arrow
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1 32
Mobilise Drill
Activity
2 3
Duration (Days)
ij
i
j
Event
Event

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11
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1 5432
Prepare
wood
Apply
undercoat
Wait for
undercoat
to dry
Apply
gloss
40 mins 30 mins120 mins30 mins

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Nodes
The circles are called nodes and show:
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The earliest start time
•This shows the earliest time
that the next task can start
The latest finish time
•This shows the latest time
that a task can finish without
delaying the next task
The node number
•This makes it easier to
follow a path through a
network
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The arrows in the network show tasks
 Tasks use up resources (e.g. time)
 Activities are dependent on each other
i.e. gloss cannot be applied until the
undercoat has dried
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Prepare
wood

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 There will be at least one critical path extending
from the beginning to the end of the project.
 Tabulate activity times (early start, early finish,
late start, late finish, total float, and free float) that
can help you schedule resources and identify
schedule flexibility.
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Activity on Node

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17East Africa University, Faculty of Information Science and Technology, Department of Computer Science

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20 East Africa University, Faculty of Information Science and Technology, Department of Computer Science

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Definitions
 Float (slack) - amount of time that a task can be delayed
without causing a delay to:
 subsequent tasks (free float)
 project completion date (total float)
 Critical path is the sequence of activities which add up to
the longest overall duration. It is the shortest time possible
to complete the project.
 Any delay of an activity on the critical path directly
impacts the planned project completion date (there is
no float on the critical path).
 A project can have several, parallel, near critical paths. An
additional parallel path through the network with the total
durations shorter than the critical path is called a sub-
critical or non-critical path.
 Critical activity – activity with zero float
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Group Practice
All in one group work:
 Discuss Critical path and the sequence
of activities which add up to the
longest overall duration.
 Do some Critical Path Analysis
practrices using Activity on Node

Practical session 1 (critical path analaysis)

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