Network diagrams in context

Transcription

1 PM Network diagrams in context SOW CHARTER SCOPE DEFINITION WBS circulation, negotiation, translation WBS WP à activities estimation Time Cost GANTT PERT AOA AON planning, resource alloca7on, cost alloca7on, control Mainly PMBOK chapter 6

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3 Network diagrams WBS

4 PERT, what does it state for? They are like WBS?

5 PERT Program Evalua/on & Review Technique

6 WBS GANTT PERT

7 Network Analysis (PERT Program Evalua/on & Review Technique; CPM Cri/cal Path Method) Network modula7on approach used in planning, scheduling and controlling projects. Beyond the analysis they facilitate, they represent a common ground to discuss op7ons so they are excellent communica7on tools. They facilitate thema7c brain- storming analysis Network diagrams are en7ty/rela7onship models (interrela7ons among instances of resources) usually used in project planning, namely on scheduling and 7me management Using these models we need to take into account: interrela7on of ac7vi7es (sequencing rela7ons) and rela7ons among ac7vi7es and resources (alloca7on) There are more complex models, using sta7s7cs but we will eventually address them later

8 Cri7cal Path Method (CPM) (determinis7c) A schedule network analysis technique used to determine the amount of scheduling flexibility (the amount of float) on various logical network paths in the project schedule network, and to determine the minimum total project dura7on. Early dates are calculated by means of a forward pass, using a specified start date. Late dates are calculated by means of a backward pass, star7ng from a specified comple7on date, which some7mes is the project early finish date calculated during the forward pass calcula7on. Program Evalua7on and Review Technique (PERT) (probabilis7c) A technique used to improve the accuracy of the cost or dura7on es7mates of project components when there is uncertainty. PERT uses weighted averages of op7mis7c, pessimis7c, and most likely es7mates (the well- known three- point es7mates) of the components' cost or dura7on. Different weigh7ng schemes represent different probability distribu7ons of the possible cost or dura7on of a component. For instance, the typical formula is [(op/mis/c + 4 /mes the most likely + pessimis/c) divided by 6], approximates a beta distribu7on.

9 CPM/PERT Cri7cal Path Method (CPM) DuPont & Remington- Rand (1956) Determinis7c task 7mes Ac7vity- on- node network construc7on Project Evalua7on and Review Technique (PERT) US Navy, Booz, Allen & Hamilton Mul7ple task 7me es7mates (probabilis7c) Ac7vity- on- arrow network construc7on

10 PERT elements Events (states), ac7vi7es (nature and 7me), preceding, alloca7on, context (context must always be defined and clarified) Some examples of PERT representa7on - AOA ac/vity on arrow, or ADM - arrow diagramming method; and AON ac7vity on node A,3 B,5 C,7 D,2 E,6 F,3 G,10

11 PERT elements Events (states), ac7vi7es (nature and 7me), preceding, alloca7on, context (context must always be defined and clarified) Some examples of PERT representa7on - AOA ac7vity on arrow, or ADM - arrow diagramming method; and AON ac7vity on node A,3 E,6 B,5 C,7 F,3 G,10 D,

12 Examples of different nota/ons

13 AOA - Parallel ac/vi/es signaled as we exemplify are not allowed A B A A,B B dummy

14 Task B can only be started acer ac7vity A is completed. The same with D and C A,3 B,7 C,4 D,

15 Network Analysis example AOA A,3 B,7 C,4 D,6 There is a dummy ac/vity dura7on 0 (only a logical dependency)

16 Network Analysis example AOA A,3 B,7 C,4 D, Are all paths iden7fied?

17 Network Analysis example AOA A,3 B,7 C,4 D, No, there are three paths, not two! And that makes quite a difference!!

18 Network Analysis example AOA A,3 B,7 C,4 D, Activity Duration Early St Early Fi Latest St Lat. Fi. Float A B C D Dummy

19 Network Analysis example AOA A,3 B,7 C,4 D, Activity Duration Early St Early Fi Latest St Lat. Fi. Float A B C D Dummy

20 PERTS, and projects 1. Define the project and all its ac7vi7es. The project is made of tasks and all tasks should have a single start and a single finish 2. Develop the rela7onships among the ac7vi7es. Decide which ac7vi7es must precede, which must follow others, and the ones that can be executed in parallel. If you are short in 7me try to put in parallel as much ac7vi7es as you can 3. Draw the network diagram connec7ng all the ac7vi7es. Each ac7vity is unique. Dummy ac7vi7es are immaterial in 7me but relevant in sequence, they impose logical dependences 4. You can assign 7me and cost to each ac7vity Preceded by a planning effort by the project management team. This planning effort is part of the Develop Project Management Plan process 5. Compute the longest 7me path through the network. This path is called the Cri/cal Path 6. Use the network to help plan, schedule, monitor and control the project and also as a communica7on tool documented in the schedule management plan

21 PERTS, and projects

22 PERTS, and projects

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24 Late start and backward path backward pass Early dates are calculated forwards, using the forward path. Late dates are calculated in reverse direc7on, star7ng at the date of the finishing of the project this is the backward path In this example one backward path leads us to event 3 through ac7vity B. So we have: Total project 7me (cri7cal path) = = 4. This means that the late start for ac7vity B is 4 Rela7ng to event 2 we have to evaluate two paths, Dummy and D. Through Dummy we have 4-0 = 4, this means that Dummy late start is 4 and through D we have 11-6 = 5, so ac7vity D late start is 5 Activ ity Dura tion Early St Early Fi Lates t St Lat. Fi. Float A,3 3 B,7 A B C D Dum my DUMMY,0 C,4 D,6 2 4

25 So you already have the rule to compute early starts and late starts. Early starts are computed in the forward path from the beginning to the end, adding dura7on and late starts are computed in the backwards path, subtrac7ng dura7on from the end Project management tools compute this for you, you just have to manage according to situated condi7ons (environment, resources, risk, )

26 Your project is to design and develop an electric motor. Ac7vity dura7ons and predecessors are iden7fied at the following table. A) construct a PERT; B) Which is the dura7on of every path? Which path is the cri7cal one? C) What happens if ac7vity E dura7on becomes 8? Ac7vity dura7on predecessor A 10 - B 20 - C 4 - D 2 A E 10 B,C F 8 B,C G 4 B,C H 2 C I 6 G,H J 2 D,E

27 Network Analysis example AOA Ac7vity dura7on predecessor A 10 - B 20 - C 4 - D 2 A E 10 B,C F 8 B,C G 4 B,C H 2 C I 6 G,H J 2 D,E

28 Network Analysis example AOA Ac7vity dura7on predecessor A 10 - B 20 - C 4 - D 2 A E 10 B,C F 8 B,C G 4 B,C H 2 C I 6 G,H J 2 D,E 8 paths CP

29 Network Analysis example AOA à AON AOA A,3 B,7 C,4 D,6 AON B A,3 B,7 END C,4 D,6 With AON you don t have dummies

30 Network Analysis example AON A,10 D,2 Ac7vity dura7on predecessor A 10 - B 20 - C 4 - D 2 A E 10 B,C F 8 B,C G 4 B,C H 2 C I 6 G,H J 2 D,E B B,20 C,4 E,10 F,8 G,4 H,2 J,2 I,6 END ADJ 14 BEJ 32 BF 28 BGI 30 CEJ 16 CF 12 CGI 14 CHI 12

31 Question exam type You have an activity with an early start in week 6, an early finish in week 10, a latest start in week 14 and a latest finish in week 18. The slack of this activity is? A) Four weeks; B) Six weeks; C) Eight weeks; D) Twelve weeks