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					PERT - CPM

      By
Naveed I. Salman


 naveedis@hotmail.com, 03215168779   1
             Quote

A dream is just a dream. A goal is a
 dream with a plan and a deadline.
        - Harvey Mackay


                                       2
      Project Management

What is a project?
 A project is a series of activities
 directed toward the accomplishment
 of a desired objective.




                                       3
            Project Management
• Characteristics of Projects
   – Unique, one-time operations
   – Involve a large number of activities that must be planned and
     coordinated
   – Long time-horizon or critical time constraints
   – Goals of meeting completion deadlines and budgets
• Examples
   – Building a house
   – Planning a meeting
   – Introducing a new product




                                                                     4
           Project Scheduling
             Management
Project scheduling is concerned with the
    techniques that can be employed to manage
    the activities that need to be undertaken
    during the development of a project.
Scheduling is carried out in advance of the
    project commencing and involves:
  –   identifying the tasks that need to be carried out;
  –   estimating how long they will take;
  –   allocating resources (mainly personnel);
  –   scheduling when the tasks will occur.




                                                           5
                   Project Scheduling
                      Management
• Once the project is underway control needs to be
  exerted to ensure that the plan continues to represent
  the best prediction of what will occur in the future:
    –   based on what occurs during the development;
    –   often necessitates revision of the plan.

•    Effective project planning will help to ensure that the
    systems are delivered:
    –   within cost;
    – within the time constraint;
    – to a specific standard of quality.




                                                               6
     Project Management Tools

• Older simpler - Gantt Chart
• More modern – CPM/PERT
• Newest – Microsoft Project ™




                                 7
                         Gantt Chart
                                  Days After Start
             Start   5    10   15  20    25    30      35   40   45   50
Activity

Foundation
Framing

Plumbing
Electrical

Wall Board
Siding

Paint Interior
Paint Exterior

Fixtures

             Start   5   10    15    20   25     30    35   40   45   50
                                    Days After Start
                                                                           8
     Advantages of Gantt
1. Easy to understand
2. Easy to construct




                           9
       Project Management
• PERT - Project Evaluation and Review
  Technique

• CPM - Critical Path Method




                                         10
                        PERT/CPM
• PERT
   –  Program Evaluation and Review Technique
   – Developed by U.S. Navy for Polaris missile project
   – Developed to handle uncertain activity times

• CPM
   – Critical Path Method
   – Developed by Du Pont & Remington Rand
   – Developed for industrial projects for which activity times generally
     were known
• Today’s project management software packages
  have combined the best features of both
  approaches.

                                                                            11
  Project Management PERT/CPM

• In projects that are non-repetitive information
  necessary for control is sparse, non-existent
  or only marginally relevant.
• Project control then requires:
   – A logical methodology showing the required tasks
     and the interrelationships of these tasks
   – Estimation of the resources required for each
     activity/step
      •   Time
      •   Money
      •   Personnel
      •   Equipment
                                                        12
      PERT/CPM Type Projects
•   Construction
•   Engineering
•   Software Development
•   Equipment Cut-over
•   Anything with many interdependent
    activities/steps


                                        13
           Network Diagram
• Activities

• Events




                             14
             ACTIVITIES
• Activities are shown as lines or arrows


• Activities require time and other
  recourses




                                            15
                Activities
• Some may be executed simultaneously
     DO THIS


    AND AT THE SAME TIME DO THAT

• Some cannot be performed until others
  are completed



                                          16
        Situations in network diagram
             B
    A                     A must finish before either B or C can start
                     C
    A
                 C        both A and B must finish before C can start
B
    A                C     both A and C must finish before either of
    B                      B or D can start
                     D

A        B
                         A must finish before B can start
        Dummy            both A and C must finish before D can start
C                                                                17
                 D
     EVENTS


• Events or nodes or mileposts or circles
• They consume NO time and show
  connections between activities
• Every PERT/CPM chart has one Start
  event and one end event

                                            18
    CPM -Critical Path Method
• A tool to determine duration based on the
  identification of the Critical Path through
  the activity network.
• Times are known with some high degree
  of certainty.
• Management can determine the duration
  of a project and concentrate efforts on
  Critical Path activities.

                                                19
   PERT Program Evaluation and
       Review Technique
• Time are NOT known well (uncertainty)
• Statistics used to estimate probability of
  finishing within a given time




                                               20
The Six Steps Common to PERT & CPM
  o   Define the project and identify each activity
  o   Develop relationships among the activities.
      (Decide which activities must precede and
      which must follow others.)
  o   Draw the network connecting all of the
      activities
  o   Assign time and/or cost estimates to each
      activity
  o   Compute the longest time path through the
      network. This is called the critical path
  o   Use the network to help plan, schedule,
      monitor, and control the project                21
         Simple CPM Chart


START               1                  END

        Open Book       Read Chapter




                                             22
            Calculating times
                          4
                                        3
              4
        2


START                                         END


               3                        4
                              2



  • Time for top route = 2 + 4 + 4 + 3 = 13
  • Time for bottom route = 2 + 3 + 2 + 4 = 11


                                                 23
             Critical Path
                           4
                                        3
              4
        2


START                                         END


               3                        4
                               2



  • Time for top route = 2 + 4 + 4 + 3 = 13
  • Time for bottom route = 2 + 3 + 2 + 4 = 11
  • Top is Critical path
                                                 24
                                Slack time
         No
         SLACK
         here                                 4
                                                               3
                           4
          2



START                                                              END


                           3                                   4
                                                  2



  • Time for top route = 2 + 4 + 4 + 3 = 13
  • Time for bottom route = 2 + 3 + 2 + 4 = 11
  •     For activities not on Critical path           Slack time = 2
                                                                       25
                                     Slack time
                                                         4
                                                                                     3
                              4
           2


START                                                                                    END


                               3
                                              B                                      4
                                                             2


  • For activities not on critical path the slack time is extra time
    that could be used if necessary
  • If event B is reached in 6 days is there a significant
    problem?
  •     No, not if the cause was the activity that should have taken 3 days took 4
  •     Yes, if the cause was the 2 day activity following start took 3 days

                                                                                          26
      Review of PERT/CPM
• A project network can be constructed to
  model the precedence / order of the
  activities and the relationship between
  activities.
• The Lines of the network represent the
  activities.
• The Circles of the network show
  events.
• A critical path for the network is a path
  consisting of activities with zero slack.   27
       PERT Activity Times

• 3 time estimates


                           
  – Optimistic times (a)
  – Most-likely time (m)
  – Pessimistic time (b)
• Follow normal distribution
• Expected time: t = (a + 4m + b)/6
• Variance of times: v = ((b - a) /6) 2

                                          28
                    Time Estimation
• Estimates of Activity Times Activity time is the
  elapsed time required for an activity. Estimating
  activity times is probably one of PERT’s most critical
  features.
• Managers are reluctant to commit themselves to a
  rigid time schedule.
   – Weather conditions, alone, prompt uncertainties and make it
     difficult for the manager to develop a single time estimate.
     However, experience has shown that managers are less
     reluctant if allowed three different estimates, especially when
     they understand PERT and how the concept of three time
     estimates is used. PERT, therefore, calls for not one, but
     three estimates of every activity time and allows the
     manager an opportunity to express his uncertainty about the
     possible time range of an activity.                             29
                 Time Estimation
• All three time estimates assume a static level of
  resource use. The estimates should be as good as
  possible because PERT results depend directly on
  them. To obtain accurate estimates is not easy. It will
  require research, collaboration with planning team
  members, and homework.
• Simple guesswork is inadequate.
   If some time estimates are mere guesses, the manager will
     soon realize that they jeopardize or needlessly extend
     the project schedule date. Once the estimator realizes
     that his contributions are a small, but vital component of
     the PERT system, he will try to steadily improve his
     estimates. In short, guesswork will not replace
     intelligently derived estimates.

                                                                  30
             Time Estimation

• The person most familiar with the operation
  and requirements of each activity should
  submit the three time estimates. These
  should meet the following criteria:
   – 1) Optimistic Time -- the minimum time
     period in which the activity can be
     accomplished, i.e., the time it would take to
     complete it if everything proceeded better
     than expected. (labeled a.)


                                                     31
               Time Estimation
2) Most Likely Time -- the best estimate of the time
   period in which the activity can be accomplished, i.e.,
   the estimate submitted if one (only) had been
   requested. (labeled m.)
3) Pessimistic Time -- the maximum time period it
   would take to accomplish the activity, i.e., the time
   required if everything went wrong, excluding major
   catastrophes. (labeled b.)




                                                             32
          Time Estimation
• It is acceptable to state these estimates
  in days, weeks, or months as long as
  the measure is used consistently.
  Once made, activity time estimates are
  firm and should not be changed without
  a change in the nature and scope of the
  activity or in the level of resources
  allocated to it. The following time
  relationships must be adhered to: ... a
  equal or less than m which is equal or
  less then b                               33
         Some Important Points
• The process is no better than the network and the time
  estimates
   – People do this
   – Knowledgeable people must determine which activities must
     proceed others and the time each activity will require
   – Some careful estimates are still better than no information


• The resulting schedule should be a normal schedule.
   – A Crash schedule exists when extra resources are added to
     reduce time.




                                                                   34
   Advantages of PERT/CPM
• Especially useful when scheduling and controlling
  large projects.
• Straightforward concept and not mathematically
  complex.
• Graphical networks aid perception of relationships
  among project activities.
• Critical path & slack time analyses help pinpoint
  activities that need to be closely watched.
• Project documentation and graphics point out who is
  responsible for various activities.
• Applicable to a wide variety of projects.
• Useful in monitoring schedules and costs.


                                                        35
                  Benefits of CPM/PERT
 •   Useful at many stages of project management
 •   Mathematically simple
 •   Give critical path and slack time
 •   Provide project documentation
 •   Useful in monitoring costs

 CPM/PERT can answer the following important
 questions:
•How long will the entire project take to be completed? What are the
risks involved?
•Which are the critical activities or tasks in the project which could
delay the entire project if they were not completed on time?
•Is the project on schedule, behind schedule or ahead of schedule?
•If the project has to be finished earlier than planned, what is the best
way to do this at the least cost?                                     36
                          Sandwich PERT Chart

A.   Toast Bread
B.   Make an egg omelet
C.   Spread butter on toast
D.   Spread omelet on toast


                                              1 minute
         3 minutes     2 minutes   1 minute
                                                           7 minutes


                                                         5 minutes




                                                                       37
             Practice Exercise
Activities   Pre -       Duration in Cost in
             Activity    Weeks       (000) Rs
      a            -          6           2
      b            -          8           3
      c            -          5           5
      d            b         13           7
      e            c          9          11
      f            a         15           9
      g            a         17           5
      h            f          9           8
      i            g          6           4
      j           d, e       12           6
       Questions / Answers
• ??




           naveedis@hotmail.com, 03215168779   39
                        Solution
• Critical Path                     f, 15


                                     g, 17                         h, 9
         a, 6
                                                       i, 6

           b, 8
                                    d, 13                  j, 12

                c, 5
                                  e, 9

                       naveedis@hotmail.com, 03215168779                  40
Your Presenter
      • Naveed I. Salman
        M. Sc (Mathematics),
        MCS, MIT, M.A.(EPM)

      • naveedis@hotmail.com
      • 0321 5168 779




                               41
   The End

    Thank You




naveedis@hotmail.com, 03215168779   42

				
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