4.2 project management- scheduling

7/30/2019 4.2 Project Management- Scheduling

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PPROJECTROJECT MMANAGEMENTANAGEMENT

AANDND AAPPRAISALPPRAISAL

PGDM – III PGDM – III

SemSem

Chandra MohanChandra Mohan



Project Scheduling- IntroductionProject Scheduling- Introduction

• Scheduling: In simple terms Scheduling is timesequence of activities. It is a process of listing

down step by step, in sequential order the

activities involved in the implementation of a

project. –It is a sub-phase of planning.

–It is an exercise of integrating time, resources and

work elements in the most efficient manner to achieve

the specified objective function. –Scheduling interrelates Availability of resources and

their economic distribution, time duration of individual

activities, and for the total work



An Analogy to Project Planning An Analogy to Project Planning

• Project Plans are like road maps: –Tells us how to get there where you want to go

(Objective)

– Also tells us how much progress has been made

–Work packages / tasks/ activities are building blocks tobuild this road

– Along the way are signposts called events and

milestones (that shows the progress of a project)

–Events and milestones are a point in time, whereas

workpackages are an actual process



Types of SchedulingTypes of Scheduling

• Forward Scheduling: –Starts as soon as clearance is available for an activity

–Can finish even before the required due date

• Backward Scheduling:

–Starts backward from the required due date of

finishing the activity and thus start date/time is

calculated

–Start time thus calculated is the latest starting date

–Based on the philosophy “finish economically when

required”



Planning and Scheduling TechniquesPlanning and Scheduling Techniques

• Main techniques of project planning andscheduling are as follows:

–Bar chart (Also knows as Gantt Chart)

–Networking techniques

•PERT (Programme Evaluation and Review Technique)•CPM (Critical Path Method)

–Line of Balance (LOB)

• Some other not so common techniques are:

GERT, Liner programming and Simulation



Constructing a Project Network- TerminologyConstructing a Project Network- Terminology

• Terminology –Event: Generally an event refers to starting or ending

point of an activity. It is just a point in time and does

not consume any time.

•Head event• Tail event

–Constraints: Constraints refer to inequalities which

establishes relationship between the sequence of

network activities. Eg. There may be a condition that

unless an activity is completed, the other activity can

not be started. X < Y will mean unless activity X is

completed, Y cant be started.



Constructing a Project NetworkConstructing a Project Network

• Activity: It is a work task, something that has tobe done. It can be a unit of work at any level of

the WBS.

• Two common approaches for constructing

network diagrams are: – Activity-on-Node (AON): Used in CPM analysis

•Uses a Node to depict an activity

– Activity-on-Arrow (AOA): Used in PERT analysis

•Uses an arrow to depict an activity



Construction of Network DiagramConstruction of Network Diagram

• Basic Rules to Follow in Developing ProjectNetworks:

–Networks typically flow from left to right.

– An activity cannot begin until all of its preceding activities

are complete.

– Arrows indicate precedence and flow and cannot cross

over each other (unless completely unavoidable)

–Identify each activity with a unique number; this number

must be greater than its predecessors.

–Looping is not allowed.

–Conditional statements are not allowed.

–Use common start and stop nodes.



How to construct an AON networkHow to construct an AON network

• To construct an AON project network, start bydrawing the first activity in the project as the

beginning node.

• From this node, draw lines to the activities that

happen next• Before activities can be included in a network,

their relationships to each other must be known:

–What activities are its predecessors? –What activities are its successors?

–What activities can be done at the same time?



Example of AON- Partial NetworkExample of AON- Partial Network



Activity on Arrow (AOA)- Building Blocks Activity on Arrow (AOA)- Building Blocks



Activity-on-Arrow (AOA) Fundamentals Activity-on-Arrow (AOA) Fundamentals



How to construct an AOA networkHow to construct an AOA network

• Also called as AOL (Activity on Line method)

• Here an activity can be defined in two ways, either byname or by the nodes at the ends.

• To construct an AOA network, start by first drawing anode to represent the origin event, representing the startof first activity of the project

• From this node, an arrow is drawn to another node,representing finish of the first activity

• Activities to be performed next are then added insequence or in parallel from the last node

•Dummy activities are used in AOA networks, to illustrateprecedence relationship – It serves only as connector and represents neither work nor time – Solves the problem/confusion of information captured by an

event node.



Example of AON- Complete NetworkExample of AON- Complete Network



AON versus AOA AON versus AOA

• No dummy activities are required for AON andthus AON are simpler to construct

• Lags can be incorporated in AON while they are

difficult to do in AOA

• Since AOA diagrams use line segments to

represent the flow of work and time, it is easy toconstruct schedules that are similar in

appearance to GANTT charts



Questions- Network DiagramsQuestions- Network Diagrams

Question 1: A project has to be undertaken bycompleting activities A to I. Following information

is given regarding precedence relationship

between activities.

– A < D, E –B, D < F

–C < G

–B, D, G < H

–B, D, F, G < I

On the basis of above information, prepare a

network diagram for given project.



Questions- Network DiagramsQuestions- Network Diagrams

Question 2: The following is known for a project:

Draw/ Calculate:

a)Network diagram of the project

b)Critical path

Theoretical questions can also be framed fromNumerical/practical topics. Ex: Ques 3

Question 3: What is the procedure of determining Critical

Path?

Activity 1-2 1-3 2-3 2-4 3-4 4-5

Duration 20 25 10 12 6 10



Computations in Network DiagramsComputations in Network Diagrams

• Forward Pass—Earliest Times –How soon can the activity start? (early start—ES)

–How soon can the activity finish? (early finish—EF)

–How soon can the project finish? (expected time—ET)

• Backward Pass—Latest Times

–How late can the activity start? (late start—LS)

–How late can the activity finish? (late finish—LF)

–Which activities represent the critical path?

–How long can it be delayed? (slack or float—SL)



Calculations for ES, EF and LS, LFCalculations for ES, EF and LS, LF

• ES: Early start of an activity depends on thecompletion time of an activity’s immediate

predecessors. It can be found by summing up of

duration (ES time each predecessor activity +

duration of immediate predecessor) of eachpredecessor activity along the path. ES reflects

the total time along the longest path

• LS: Late times: Latest allowable times that the

activity can be started and finished withoutdelaying the completion of project.




• Network activities –ES: early start

–EF: early finish

–LS: late start

–LF: late finish

• Used to determine –Expected project duration

–Slack time (Total Slack and Free Slack)

–Critical path




• Total Slack is defined as amount of variationbetween when an activity must take place (LS)

and when it can take place at earliest (ES)

–Total Slack = LS – ES or LF – EF

–For activities lying on critical path ES = LS and thusslack = 0

• Free Slack is the amount of time an activity can

be delayed without affecting the start times of

any successor activities. –Free Slack = ES (of earliest successor) – EF (of given activity)



PERTPERT

• PERT (Program Evaluation and Review Technique), is

used in projects where there is uncertainty associatedwith the nature and duration of activities. – PERT analysis is on the basis that a small set of activities, which

make up the longest path through the activity network control theentire project.

• In AOA, AON methods computations are done using thebest time estimates. PERT however addressesuncertainty in duration by using three time estimates-optimistic, most likely and pessimistic. These estimatesare used to calculate the Expected time for an activity – Optimistic time: The minimum time an activity could take-the

situation where everything goes well – Pessimistic time: it is the maximum time an activity could take-

when bad luck is encountered at every stage – Most likely: Normal time to complete the job



PERT: Time Estimates for a ProjectPERT: Time Estimates for a Project

• Optimistic time

–Time required under optimal conditions

• Pessimistic time

–Time required under worst conditions

• Most likely time –Most probable length of time that will be required

te =to + 4tm +tp

6

te = expected time

to = optimistic time

tm = most likely time

tp

= pessimistic time

• Expected time (te)



PERT: VariancePERT: Variance

• Variance: V or σ2 (variance) is a measure of variability in the activity completion time:

• Larger is the value of V, the less reliable te, andthe higher likelihood that the activities will becompleted much earlier or much later than t

e.

• Total time of a project is summation of expected time of activities on critical path

• Variation of Project is computed as sum of thevariances of the activity durations along thecritical path

V = σ2 =(tp – to)

2

36



PERT : Path probabilitiesPERT : Path probabilities

Optimistictime

Most likelytime (mode)

Pessimistictime

to tptm te

Z indicates how many standard deviations of the path distributionthe specified time is beyond the expected path duration .

Z =Specified time (Ts) – Path mean(Te)

Path standard deviation (σ

)



PERT- ExamplePERT- Example

Ques: The details of a project are given below:

Determine the probability of completing the project in 51weeks

Activity Nodes Optimistic time Pessimistic time Normal time

A 1-2 4 8 6

B 2-3 5 15 7

C 2-4 4 12 8

D 3-6 15 25 20

E 3-5 10 26 18

F 4-6 8 16 9

G 5-7 4 12 8

H 6-7 1 3 2

I 7-8 6 8 7



PERT- ExamplePERT- Example

Solution: –Step I: Prepare the network diagram and determine

the critical path

–Step II: compute expected time and variance for each

activity –Step III: Calculate variance for Critical path, and thus

find standard deviation

–Probability of completing the project in 51 weeks :

•Z = (Specified time – expected time) / Std dev of critical path

•Check for value of Z in probability distribution table

4.2 project management- scheduling

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