01. Critical Path Analysis - Latest Jan 09

8/11/2019 01. Critical Path Analysis - Latest Jan 09

1/51

1

HND UNIT 1

BUSINESS MANAGEMENT TECHNIQUES

CRITICAL PATH ANALYSIS


2/51

2

Critical path analysis (CPA) is a powerful tool

to help you schedule and manage complex

projects.

History

Developed in the 1950s to control large

defence projects and has been used eversince.

CRITICAL PATH ANALYSIS


3/51


4/51

4

Advantages of CPA over Gantt Charts

Formally identifies tasks, which must be completed ontime for the whole project to be completed on time.

Identifies tasks, which can be delayed for a while if

resources need to be allocated to catch up on missed

tasks.

Identifies the minimum length of time to complete a

project.

It helps to identify which tasks need to be accelerated if

you need to run an accelerated programme.


5/51

5

Disadvantages of CPA over Gantt Charts

Relation of tasks to time is not

immediately obvious i.e. no timeline.

Therefore CPA charts are more difficult to

understand if you are not familiar with

technique.


6/51

6

Activity

Is a task or function that consumes time and other

resources.

Event

Consumes no resources, especially no time. An event can

be considered to represent a point in time or the

representation of the status of a project at a particular

instance i.e. project starts.

CPA chart nomenclature


7/51

7

Drawing a CPA chart

List all activities in the plan

Show the earliest start date

Estimate the length of time for each task

Determine whether the tasks are parallel or

sequential. If sequential show what task they are

dependent upon.

Plot the activities in a graphical depiction of the

project i.e. tasks that make up the project andthe logical relationships between them

represented by symbols


8/51

8

There are two types of logic diagrams:-

Types of Diagram

Circle and arrow.

Precedence diagrams.


9/51

9

Arrow Diagrams

Diagram is made out of arrows and nodes plusnumbers and letters for calculation and labelling

purposes.

The arrows represent the actual activity of task.

The nodes represent the point in time (event)

when activities start and finish.


10/51

10

Precedence Diagrams

Activities are shown as nodes. Arrowsrepresent activity links or logical

relationships.

Activity links can have lead times i.e. paint

drying etc, links consume no other resource

than time.

Lead times can be zero positive or

negative.


11/51

11

Diagram differences

The two diagrams are fundamentallydifferent in the methods of graphicallyrepresentation but they depict the

same information.

However precedence diagrams areconsidered easier to develop and

understand.


12/51

12

EARLIEST

START

LATESTSTART

DURATION

ACTIVITY DESCRIPTION

EARLIEST

FINISH

CRITICAL PATHSLACK TIME LATESTFINISH

PRECEDENT DIAGRAM


13/51

13

EARLIEST

START

LATESTSTART

DURATION


EARLIEST

FINISH

CRITICAL PATHSLACK TIME LATESTFINISH

PRECEDENT DIAGRAM

INSERT DESCRIPTION OR NUMERICAL VALUES


14/51

14

PRECEDENT DIAGRAM

EARLIEST

START

LATEST

START

DURATION


EARLIEST

FINISH

CRITICAL PATH

SLACK TIME

LATEST

FINISH

EARLIEST

START

LATEST

START

DURATION


EARLIEST

FINISH

CRITICAL PATH

SLACK TIME

LATEST

FINISH

FINISH TO START - MOST COMMON


15/51

15

EARLIEST

START

LATEST

START

DURATION


EARLIEST

FINISH

CRITICAL PATH

SLACK TIME

LATEST

FINISH

EARLIESTSTART

LATESTSTART

DURATION


EARLIEST

FINISH

CRITICAL PATH

SLACK TIMELATESTFINISH

START TO START

PRECEDENT DIAGRAM


16/51

16

EARLIEST

START

LATEST

START

DURATION


EARLIEST

FINISH

CRITICAL PATH

SLACK TIME

LATEST

FINISH

EARLIEST

START

LATEST

START

DURATION


EARLIEST

FINISH

CRITICAL PATH

SLACK TIME

LATEST

FINISH

START TO FINISH

PRECEDENT DIAGRAM


17/51

17

EARLIEST

START

LATEST

START

DURATION


EARLIEST

FINISH

CRITICAL PATH

SLACK TIME

LATEST

FINISH

EARLIEST

START

LATEST

START

DURATION


EARLIEST

FINISH

CRITICAL PATH

SLACK TIME

LATEST

FINISHFINISH TO

FINISH

PRECEDENT DIAGRAM


18/51

18

EARLIEST

START

LATEST

START

DURATION


EARLIEST

FINISH

CRITICAL PATH

SLACK TIMELATEST

FINISH

EARLIEST

START

LATEST

START

DURATION


EARLIEST

FINISH

CRITICAL PATH

SLACK TIMELATEST

FINISH

FINISH TO START WITH PRECEDENT

PRECEDENT

TIME

6

PRECEDENT DIAGRAM


19/51

19

EARLIEST

START

LATEST

START

DURATION


EARLIEST

FINISH

CRITICAL PATH

SLACK TIMELATEST

FINISHEARLIEST

START

LATEST

START

DURATION


EARLIEST

FINISH

CRITICAL PATH

SLACK TIMELATEST

FINISH

EARLIEST

START

LATEST

START

DURATION


EARLIEST

FINISH

CRITICAL PATH

SLACK TIMELATEST

FINISH

PRECEDENT DIAGRAM

EARLIEST

START

LATEST

START

DURATION


EARLIEST

FINISH

CRITICAL PATH

SLACK TIMELATEST

FINISH

EARLIEST

START

LATEST

START

DURATION


EARLIEST

FINISH

CRITICAL PATH

SLACK TIMELATEST

FINISH


20/51

20

Early start (ES) - the point in time that all preceding activities

have been completed.

Early finish (EF) - the earliest that all work started with an early

start can be completed.

EF = ES + D

Late finish (LF) - the point in time that all work involved in theactivity must be completed in order to avoid delaying subsequent

activities.

Late Start (LS) - the point in time by which an activity must be

started in order to avoid delay to following activities. LS = LF-D

Project Duration (D) - is the aggregate combination of all the

activities along the critical path of the project.

Activity Times


21/51

21

Is the path representing the combination of

activities any one which delayed will cause a

delay to the project.

It is the longest time through the network.

Critical activities have zero total float.

Critical path


22/51

22

Total float

Total float or slack time is the amount of timeby which the start or finish of an activity canbe delayed without delaying the projectcompletion.

TF = ES LF D, or

TF = LF EF, or

TF = LS - ES (PREFERRED OPTION)


23/51

23

Free float

The maximum amount of time that anactivity can be delayed beyond its earlystart without delaying the early start ofany other activity immediately following

that activity.

FF = ES succeeding - EF preceding


24/51

24

Networks have to be solved in two passesa forward pass and a backward pass.

Dangling activities - all activities should

have at least one preceding activity andat least one succeeding activity except

from start and finish.

Lines CANNOTcross one another and

should minimise clutter.

Some Rules of Logic Diagrams


25/51

25

Time - working days i.e. overall duration

Man days - days people work

Paint drying days

Money costs sales and profit

Raw materials

Actual numbers of people

Estimating Resources


26/51

26

Man-days

Are the number of people performing an

activity multiplied by the working day or

duration.

The number of days that an activity willtake until completed.

To identify these requirements a numberof estimating techniques must be used.


27/51

27

Comparative estimates - use data fromcomparable projects i.e. against figures

recorded cost +/-15%

Feasibility estimates - total quotations foreach component part.

i.e. you can calculate how much paint a

ship will require to be fully coated with a

primer, base coat and top coat.

ESTIMATING TECHNIQUES


28/51

28

ESTIMATING TECHNIQUES

Ballpark estimates - are based on judgementand luck. +/- 25%.

Percentage estimates - are models based on

progress to date compared with otherprojects.

i.e. - At this point in time I have spent 10 and

I am 10% through the project hence projectcosts are 100.


29/51

29

Ballpark

Twice the optimistic plus four times

pessimistic add the most likely and divide by 7

Weight time estimates

Team experience/size

if very experienced reduce estimates by 10%

If limited experience add 10%

Rules of


30/51

30

Rules of

Customer support/understanding

Great support reduce by 10%Limited support add 10%

Little support add 20%

Novelty of project

If some new add 10%If all new add 20%


31/51

31

Rules of

Number of customers involved or number of

organisations

If 2 add 10%

If 3-4 add 20%

If 5 or more add 40%


32/51

32

Percentage of time spent on other work by ateam member

10-30% add 10% to estimates

30-50% add 20%More than 50% add 30%

Project plan complexity

If simple reduce by 10%

If very complex add 10%

Rules of


33/51

33

Is a variation on critical path analysis. It takes a moresceptical viewof time estimated for each stage.

Time for a project stage:-

(shortest time + 4) x (likely time + longest time)6

It helps to refocus timescale needed, by giving a

reasonable estimation of time rather than theunrealistically short timescale normally

assumed/DEMANDED.

Programme Evaluation and Review Technique (PERT)


34/51

34

SETTING OUT THE ANALYSIS

ANDDUMMY ACTIVITIES

SETTING OUT THE ANALYSIS AND


35/51

35

Layout a rough diagram of the project/Task

flow.

Ensure that you have the order of projectactivity shown in the correct order.

Label activities A,B etc.

In an exam you will be given numerical

values.

SETTING OUT THE ANALYSIS ANDDUMMY ACTIVITIES



36/51

36


Connect activities together using flow lines

REMEMBER that flow lines cannot cross.

Think of the analysis as a pipeline diagram or

piping system pumping manyDIFFERENTtypes

of fluid.

Different fluids cannot travel in the same pipe

andcannot cross connect.


37/51

37

Start with a START( EVENT) box and finish

with a FINISH(EVENT) box

If lines cross connect use a DUMMYbox, an

EVENTblank box, to connect the paths.



38/51

38


Analyze the project time thus:-

Start box

Box AStart time plus duration =finish time

Box B

Start time = previous box finish time.Finish time = start time plus duration etc.



39/51

39

NOTESometimes between boxes you have a PRECEDENCE

time: this refers to a SLACK time period that occurs

after an ACTIVITY/Task has finished

Typically this could be: paint drying, concrete setting,

waiting for tides etc.

This precedent must be added on to the end of the

previous activity in order to evaluate total time.

When more than one previous activity connect to the

next box, then the HIGHEST finish time becomes the

next start time.


ANALYSIS


40/51

40

Project time is evaluated by ADDING duration time,

going from left to right, to arrive at the highest number

for evaluating the project time.

LOWEST + DURATION = HIGHEST

CRITICAL PATH ANALYSIS is established by moving fromright to left and using the highest number as a start

point and SUBTRACTING duration time to arrive at

LATEST START TIME and thus assess SLACK TIME.

When SLACK Time is ZERO, then this activity is CRITICAL

and you have found a CRITICAL path.

ANALYSIS

ACTIVITY DESCRIPTION OF ACTIVITY IMMEDIATE PREDECESSOR DURATION IN DAYS


41/51


A Conduct feasibility study No 3

B Find potential customer for existing car A 14

C List possible models A 1

D Research all possible models C 3

E Conduct interviews with mechanics C 1

F Collect dealer propaganda C 2

G Compile and organise all pertinent information D, E, F 1

H Choose top three models G 1

I Test drive all three choices H 3

J Gather warranty and financing information H 2

K Choose one car I, J 2

L Compare dealers and choose dealer K 2

M Select colour and goodies options L 4

N Test drive first choice again-CHECK IMPRESSIONS L 1

O Purchase new car B, M, N 3

CONCLUSION


42/51

Critical Path Analysis is an effective and powerful

method of assessing:-

CONCLUSION

What tasks must be carr ied out.

Where paral lel activity can be performed.

The shortest time in which you can complete a project .

Resources needed to execute a project.

The sequence of activities, schedul ing and timings involved.

Task pri ori ties- reallocation of resources.

The most eff icient way of shortening time on urgent projects.


43/51

43

CONCLUSION

An effective Critical Path Analysis can make

the difference between success and failure on

complex projects.

It can be very useful for assessing the

importance of problems faced during the

implementation of the plan.

CAR PURCHASE


44/51


A Conduct feasibility study No 3

B Find potential customer for existing car A 14

C List possible models A 1

D Research all possible models C 3

E Conduct interviews with mechanics C 1

F Collect dealer propaganda C 2

G Compile and organise all pertinent information D, E, F 1

H Choose top three models G 1

I Test drive all three choices H 3

J Gather warranty and financing information H 2

K Choose one car I, J 2

L Compare dealers and choose dealer K 2

M Select colour and goodies options L 4

N Test drive first choice again-CHECK IMPRESSIONS L 1

O Purchase new car B, M, N 3

CONSTRUCTION PROBLEMWORKED EXAMPLE 2


45/51

CONSTRUCTION PROBLEM

ACTIVITY DURATION WEEKS PRECEDING ACTIVITIES

A 4

B 6

C 5

D 5 A B

E 7 A B

F 4 A B C

G 3 B C

H 7 B C

J 6 D E

K 7 F

L 3 F G

M 5 H

N 4 J

P 5 K Q

Q 7 L M

R 2 N P

S 4 P

PROBLEM 3

SHIP PROJECTWORKED EXAMPLE ANSWER 3 INTRO TO MS PROJECT


46/51

SHIP PROJECT

ACTIVITY

IDENTITY

PRECEDING ACTIVITIES PRECEDENCE LINES ACTIVITY DURATION

WEEKS

PRECEDENCE TIMES

A 5 0

B A START/START 10 4

C B FINISH/FINISH 15 5D A FINISH/START 6 0

E B FINISH/START 3 2

D START/START 4

D FINISH/FINISH 5

F C FINISH/START 10 2

E START/START 3

E FINISH/FINISH 2

G D FINISH/START 5 2

Y START/START 0

Y FINISH/FINISH 0

H E FINISH/START 8 3

J F FINISH/START 3 0

X A START/START 7 3

Y X FINISH/START 7 6

Z Y FINISH/START 8 9


47/51

ACTIVITY DURATION

DAYS

PRECEDING ACTIVITIES FIXED PRECEDENCE

TIMES

START

A 7

B 2

C 15 A,B 1

D 8 A,B 4

E 10 D 2

F 2 E

G 5 E

H 8 E 4

I 2 H

J 3 I

FINISH


48/51

ACTIVITY DURATION

DAYS


TIMES

START

A 7

B 2

C 15 A,B 0

D 8 C 2

E 10 D 5

F 2 C 3

G 5 F 0

H 8 D 0

I 2 H 0

J 3 G 3

FINISH


49/51

ACTIVITY DURATION

DAYS


TIMES

START

A 7

B 2

C 15 B 0

D 8 C,A 2

E 10 D 5

F 2 E 3

G 5 F 0

H 8 0

I 2 G 0

J 3 D 3

Z 3 H, I 4

FINISH

C P h CPA


50/51

Car Purchase CPA

CRITICAL PATH = C D G H I K LM -O

Start A

330

300

C

413

403

B

17143

2036

D

734

704

EE

514

726

F

624

715

G

817

807

H

918

908

I

1239

1209

J

1129

12110

K

14212

14012

L

16214

16014

M

20416

20016

N

17116

20319

0

23320

23020

Finish

23023

23023

0 0 0

000

Total Float = LS ES = 10 days

Construction Project


51/51

51

CRITICAL PATH = BH M Q PS

Start

A

440

1177

C

550

611

B

660

600

D

1156

221117

EE

1376

22915

F

1046

15511

G

936

15612

H

1376

1306

Q

25718

25018

J

19613

28922

K

17710

25818

L

13310

18515

M

18513

18013

N

23419

32928

P

30525

30025 Finish

34034

34034

0 0 0

000

Dummy

606

11011

Dummy

606

606

R

32230

34232

S

34430

34030

j

Documents

01. Critical Path Analysis - Latest Jan 09