Activity Duration Duration Estimating Estimating
Estimate activity duration is the process of approximating the number of work periods needed to complete individual activities with estimated resources. resources.
Estimate Activity Duration •
Input: –
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Tools & Tech Techniq niques ues –
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Activity List Activity Attributes Activity Resource Requirement Resource Calendars Project Scope Statement Enterprise environmental factors (Databases and Ref. data, Productivity metrics & published commercial information Organizational Process Assets -Historical, Project Calendar, Scheduling methodology, Lesson Learnt Expert Judgment Analogous estimating (Duration, budget, size, weight & Complexity from a previous project) Parametric estimating (square footage – cost cost budget & duration) Three-point estimates (PERT) Most likely, Optimistic, Pessimistic = te = to + 4tm +tp / 6 Reserve analysis (Cater for schedule uncertainty)
Outputs –
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Activity duration estimates (@ weeks +- 2 days etc) Project document updates (activity attributes, assumptions made in developing the activity duration)
Padding: Padding is a sign of unprofessional project management
So, what is wrong with padding? ◦
A pad is extra time or cost added to an estimate.
How Project Manager can avoid Padding: ◦
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With the help of WBS work package (the WBS dictionary) activity list. Equip the estimator relevant information.
Padding: Padding is a sign of unprofessional project management! ◦
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In cases where the estimator has many unknowns, the need for a pad should be addressed through the risk management process, and the uncertainties should be turned into identifiable opportunities and threats (risks). Uncertainties should not remain hidden; instead, they need to be identified and addressed openly with the project manager.
Think about what happens if all or many of your estimates are padded: you have a schedule that no one believes. ◦
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If that is the case, why even bother creating a schedule? In the real world, we need the schedule to manage the project against, so we need it to be as believable and realistic as possible and we need to adhere to it. To be a successful project manager, you need to be able to make sure the agreed-upon project completion date (or cost) is met. It is important to understand that padding is a sign of poor project management and that it can damage your reputation.
Exercise 1
What do you need before you try to develop a schedule for your project?
o t y r t u o y e r ? o t f c e e b j o r d p e e n r u u o y o y r o f o d l e t u a d h e h W : c 1 s r a e p o l w s e n v e A d
An understanding of the work required on the project (project scope statement)
Defined activities (WBS, WBS dictionary and activity list)
The order of how the work will be done (activity sequencing)
An estimate of the resources needed (activity resource estimating)
An estimate of the duration of each activity (activity duration estimating)
Let's get more specific. You should also have:
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• • • • • •
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• •
A company calendar identifying what are the working and non-working days Imposed dates Milestones Assumptions Constraints Activity list Risk management plan-because it includes a schedule and budget for performing risk identification, qualitative risk analysis and other risk management activities Risk register-because it includes risks known to date Leads and lags
Exercise 2 Now, Please think Now, think about the real real world world and create a schedule that you will be able to stake your reputation reputation & SUGGEST What would you you need to do in order to take the estimating data and create a finalized schedule?
l l i w u o n y i t o a d h t o ? e e t l l u u d d e d e e e h n h c c s s u o a y d e e z d i t l l a u a e n o f r c w i a t o t h a h c d u e s W e . n g t n e u i a t e o e Y e r c . m d d l r n n o o a w n a t l a o d a i t e r a g t n i e u t h p t e a r m t u r i s o u t b o a y e e k h e n k t i e h a s k T t t : o a 2 t o e t e r r e l a e w b
1. 2. 3. 4. 5.
6. 7. 8. 9.
Work with stakeholders' priorities Look for alternative ways to complete the work Look for impacts on other projects Meet with managers to negotiate for resource resource availability availability Give the team a chance to approve the final schedule. They might have estimated an activity, but should also look at the calendar allocation of their estimates to see if they are feasible Adjust all the components of the project management plan Simulate the project using Monte Carlo analysis Level resources Conduct meetings and conversations conversations to gain stakeholder and management formal approval
The data available so far is put into a schedule, called the schedule model, and the project manager then performs various calculations and alternative whatif analysis to determine the optimum schedule. Schedule development is iterative and iterative and will occur many times over the life of the project (at least once per project life cycle phase).
Conflict Intensity Over the Life of a Project 0.40 0.35 y t i 0.30 s n 0.25 e t n I t 0.20 c i l f 0.15 n o C 0.10
Schedules Average Total Conflict
Manpower Technical opinions Procedures Cost Personality conflicts
0.05 0.00
Priorities
Project Formation
Early Early Phase Phases s
Middl Middle e Pha Phases
End End Phases Phases
Develop Schedule •
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Develop Schedule is the process of analyzing activity sequence, duration, resource requirements and constraints to create project schedules Input –
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Project Schedule Network Diagrams
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Activity Resource Requirements
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Resource Calendars
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Activity duration estimates Project Scope Statement
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Enterprise environment factors
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Organizational process assets
Tools & Techniques –
Schedule network analysis
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Critical path method
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Critical chain method (manage limited resources)
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Resource Leveling
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Activity List Activity Attributes
What-if scenario analysis Applying leads and lags
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Schedule compression
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Scheduling tool
Output –
Project Schedules (milestone chart, bar charts, project schedule network diagrams)
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Schedule baseline Component of project management plan with baseline start & finish dates.
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Schedule Data (resource requirement by time period in resource histogram best & worst case Project document updates (Activity resource requirements, activity attributes, calendar, risk register)
Schedule Network Analysis
PERT Critical path method Schedule compression What-if scenario analysis Resource leveling Critical chain method
PERT In PERT analysis, instead of obtaining one estimate from each expert, experts are asked to provide an optimistic, realistic and pessimistic estimate.
PERT
Optimistic Realistic Pessimistic
Expected duration
Pessimistic estimate 4 Realistic estimate Optimistic estimate 6
PERT Dialogue How long do you think it would take to send 100 surveys out?
PERT Dialogue It all depends. I have seen people do it in 6 hours and I have seen others do it in 1 hour.
PERT Dialogue But given what I know about your operations I think it will take 2 hours.
PERT Dialogue Pessimistic estimate = 6 hours Optimistic estimate = 1 hour Realistic estimate = 2 hours
Expected duration
6 4 2 1 6
15 6
2.5
PERT Formula and Example
PERT weighted average = optimistic time + 4 * most likely time + pessimistic time 6
Example: optimistic time= 8 days most likely time = 10 days pessimistic time = 24 days PERT weighted average = 8 workdays + 4 X 10 workdays + 24 workdays = 12 days 6 Therefore, you’d use 12 days on the network diagram instead of 10 when using PERT for the above example.
Take Home Lesson Estimate-Talk-Estimate and PERT method can increase accuracy of estimate of duration of activities
PERT: Example 1 Expected Activity Duration = (P+4M+O)/6 Activity Standard Deviation = P-O/6 Activity Variance = [(P-O)/6] 2
P
M
PERT or Expected duration
O
A
47
27
14
B
89
60
41
C
48
44
39
D
42
37
29
Activity Standard Deviation Activity Variance (Rance of Estimate)
Range of the estimate
Estimates are in hours. It is best to calculate to three decimal places and round to two decimal pIaces.
PERT
P
M
PERT or Expected duration
O
Activity Standard Deviation Activity Variance (Rance of Estimate)
Range of the estimate
A
47
27
14
28.167
5.500
30.250 22.667 to 33.667 or 28.167 +/- 5.500
B
89
60
41
61.667
8.000
64.000 53.667 to 69.667 or 61.667 +/- 8.000
C
48
44
39
43.833
1.500
2.250 42.333 to 45.333 or 43.833 +/- 1.500
D
42
37
29
36.500
2.167
4.696 34.3333 to 38.667 or 35.500 +/- 2.167
PERT
Note that the previous formulas relate to activities, rather than the overall project. But knowing the ranges of individual activity duration estimates is not enough to manage a project successfully; you need to understand how these ranges affect the overall project duration estimate in order to effectively address variations on your project. Range for the overall project duration estimate is not as simple as finding the range for an individual activity estimate. You start by finding the expected project duration: ◦
This is the sum of the PERT estimates (EADs, or Expected Activity Durations) for each activity on the critical path. You then find the standard deviation for the project.
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You cannot simply add the standard deviations for each activity on the critical path.
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Instead, you must calculate the variances for each critical path activity,
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Add those variances, and then take the square root of the sum of the activity variances.
So the project duration estimate range is the expected project duration (the sum of the FADS) plus or minus the project standard deviation (the square root of the sum of the activity variances).
PERT: Exercise 2
Assuming that the activities listed in Exercise 1, make up the entire critical path for the project, how long should the project take? PERT or Expecte Project Project d Standard Varianc Project Duration Deviation e Range of the Estimate
P A B C D
Project Project Duration Estimate
Activity PERT or Activity Variance Expected Standard (Rance of M O duration Deviation Estimate) Range of the estimate 47 27 14 28.167 5.500 30.250 22.667 to 33.667 or 28.167 +/- 5.500 89 60 41 61.667 8.000 64.000 53.667 to 69.667 or 61.667 +/- 8.000 48 44 39 43.833 1.500 2.250 42.333 to 45.333 or 43.833 +/- 1.500 42 37 29 36.500 2.167 4.696 34.3333 to 38.667 or 35.500 +/- 2.167 160.167 to 180.227 or 170.167 +/For Critical Path: 170.167 101.196 10.060 10.059622 PERT or Expected Duration
170.167
Project Standard Deviation
10.06
Project Variance
Range of the Estimate
101.196 160.167 to 180.227 or 170.167 +/- 10.060
The answer is 170.167 hours +I- 10.06 hours at one standard deviation.
PERT: Exercise 2 (RULES for Critical path)
The expected duration of the project, 170,167, is found by adding the PERT estimates for each of the critical path activities (in this case, all the activities listed). The +I- 10.06 represents the standard deviation of the estimate (the range of the estimate) and is found by adding the variances of the critical path activities, total of 101.196, a nd
taking the square root to get 10.060.
In order to find the standard deviation of a series of items, remember the rule. You cannot add standard deviations; you must convert standard deviations into variances, add the variances, and then take the square root of the total to convert back into standard deviation. This calculation means adding 30.250 + 64.000 + 2.250 + 4.696 and taking the square root to find 10.06. Therefore, if we add one standard deviation to the PERT total (for a 68.26 percent confidence level ; see the Quality Management), the project would not be estimated to take 170.167 hours, but between 160.107 hours and 180.227 hours. If we add two standard deviations (for a 95.46 percent confidence Ievel), the project would be estimated to take between 150.047 hours and 190.287 hours (170.167 +I- 20.12).
Critical Path Method
The critical path method includes determining the longest path in the network diagram (the critical path) and the earliest and latest an activity can start and the earliest and latest it can be completed. The critical path is the longest duration path through a network diagram and determines the shortest time to complete the project.
How does the critical path help the project manager? d o h t e M h t a P l a c i t i r C
Helps prove how long the project will take Helps the project manager determine where best to focus their project management efforts Helps determine if an issue needs immediate attention Provides a vehicle to compress the schedule during project planning and whenever there are changes Provides a vehicle to determine which activities have float and can therefore be delayed without delaying the project
Near-Critical Path
d o h t e M h t a P l a c i t i r C
In addition to the critical path, a smart project manager should be familiar with the concept of a near-critical path. This path is close in duration to the critical path. Something could happen so the critical path is shortened, or the near-critical path lengthened so the near-critical path becomes critical. The closer the near-critical and critical paths are, the more risk the project has. The project manager should spend more time and effort monitoring and controlling critical and near-critical path activities so they don't delay the project completion.
Float (Slack)
d o h t e M h t a P l a c i t i r C
Total float (slack) The amount of time an activity can be delayed without delaying the project end date or and intermediary milestone. This is the key type of float, but there are others. ◦
Please note that the terms float and slack mean the same thing.
Free float (slack) The amount of time an activity can be delayed without delaying the early start date of its successor(s). Project float (slack) The amount of time a project can be delayed without delaying the externally imposed project completion date required by the customer, management, or previously committed to by the project manager.
Float (Slack)
d o h t e M h t a P l a c i t i r C
Activities on the critical path almost always have zero float. Critical path activities that are delayed or have dictated dates can result in negative float.
Float = LS – ES
Float = LF - EF HOW
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Once you know the critical path and any near-critical paths, you can use float as a way to focus your management of a project.
Better allocation of resources. For example, let's say you have a resource who is not very experienced and you must make use of him.You can assign him, assuming he has the skill set, to work on the activity with the most float. This gives you some safety that even if his activity takes longer, the project will not be delayed. Float also helps team members juggle multiple projects.
Critical Chain Scheduling
Critical Chain Project Management (CCPM), developed by Eliyahu M. Goldratt, is a method of planning and managing projects that puts more emphasis on the resources required to execute project tasks. A Critical Chain project network will tend to keep the resources levelly loaded, but will require them to be flexible in their start times and to quickly switch between tasks and task chains to keep the whole project on schedule. ◦
Typically, CCPM case studies report 95% on-time and on-budget completion when CCPM is applied correctly.
Wake UP …. QuiZ
Can there be more than one critical path? Yes, you can have two, three or many critical paths. Do you want there to be? No, it increases risk. Can a critical path run over a dummy? Yes. Why is a dummy included in a network diagram? To show interdependencies of activities on an activity-on-arrow diagram. Can a critical path change? Yes. . How much float does the critical path have? The critical path should have zero float. Can there be negative float? Yes, it shows you are behind. Does the network diagram change when the end date changes? No, not automatically, but the project manager should investigate options such as fast tracking and crashing the schedule to meet the new date and then, with approved changes, change the network diagram accordingly. Would you leave the project with a negative float? No, you would compress the schedule.
Exercise: 1 Let's start with an exercise that uses the AOA type diagram. You can complete these exercises without using a forward and backward pass. Using the table below, draw the network diagram and answer the questions. 1) What is the critical path? 2) If the duration of Activity C-E changes to 2, what is the effect on the project?
3) What activity (activities) must be completed before Activity C-D begins? 4) If management tells you to complete the project two weeks early, what is the project float? Does the critical path change?
Exercise: 1
1)
2)
Exercise: 1 3) Start-A, A-C, and Start-B. Caution!!! The question is really trying to get you to answer Start-B because that is what the dummy is for, to show that dependency. Remember there are no oneletter activity names (e.g., not activity C, but activity AC. B-C is a dummy, not an activity. 4) The project float is -2 and the critical path would not change. This question is about project float. Remember project float compares the project length to an external due date.
Exercise 2
What is the critical path? What is the near-critical path and what does knowing this information about this project tell you? If the duration of activity Start-B changes to 4, what is the effect on the project?
Exercise 2
Start-A, A-C, C-F, F-End. It has a duration of 21 weeks.
There are two near-critical paths, each with a duration of 20. This tells you that the project has more risk than a project with only one near-critical path with a wider difference in length between the critical and near-critical paths. There will be two critical paths:
You are the project manager for a new project and have figured out the following dependencies. Activity 1 can start immediately and has an estimated duration of three weeks. Activity 2 can start after activity 1 is completed and has an estimated duration of three weeks.
Activity 3 can start after activity 1 is completed and has an estimated duration of six weeks.
Activity 4 can start after activity 2 is completed and has an estimated duration of eight weeks.
Activity 5 can start after activity 4 is completed and after activity 3 is completed. This activity takes four weeks.
Questions:
3 e s i c r e x E
1.
What is the duration of the critical path?
2.
What is the float of activity?
3.
What is the float of activity 2?
4.
What is the float of the path with the longest float?
5.
The resource working on activity 3 is replaced with another resource who is less experienced. The activity will now take l0 weeks. How will this affect the project?
6.
Using the original information, after some arguing between stakeholders, a new activity 6 is added to the project. It will take 11 weeks to complete and must be completed before activity 5 and after activity 3. Management is concerned that adding the activity will add 11 weeks to the project. Another stakeholder argues the time will be less than 11 weeks. Who is correct?
7.
Based on the information in number 6 above, how much longer will the project take?
Exercise 3 1) The length of the critical path is 18. There are two paths here:
Total Length = 18 Weeks
2) LF - EF = 14 - 9 = 5
Total Length = 18 Weeks
3) Zero 4) Five weeks. There are only two paths in this example; Start, 1, 2, 4, 5, End and Start, 1, 3, 5, End.The length of the non-critical path (Start, i,3,5, End) is 13. The length of the project is 18 and 18 - 13 is 5. The total float of the path with the longest float is
Exercise 3 5) It will have no effect. The length of path activities 1,3,5 is 13. Adding four more weeks to the length of activity 3 will take that path 17. Since it is shorter than the critical path, the critical path does not change. The length is still 18 weeks because activity 3 is not on the critical path. 6) The stakeholder. This new activity will be added to a non-critical path that has float of 5 weeks. Therefore, adding 11 weeks will make this path the new critical path. The overall effect will be that adding an activity that takes 11 weeks will only delay the project by 6 weeks. 7) Six weeks longer. (NOTE: if you answered 24, it means you did not read the question correctly!) Follow the dark line in the diagram below.
Total Length = 24Weeks
Exercise 4 1. 2.
3.
4. 5.
What is the duration of the critical path? To shorten the length of the project, the sponsor has offered to remove the work of activity E from the project, making activity D the predecessor to activities G and F. What will be the effect? What is the float of activity B? What is the float of activity E? What is the float of activity D?
Exercise 4 1) The critical path (project duration) is 33 months.
Total Length = 33 Months 2) No effect on the critical path. The paths are now:
Exercise 4
Total Length = 33 Months
3) Float B = LF - EF (or 33 - 18) = 15 4) Float E = LF - EF (or 13 - 12) = 1 5) Float D = 5 - 4 = 1 month.
Schedule Compression Who’s fault to have an
unrealistic schedule:
Many project managers think an unrealistic schedule is their boss' fault, when it is really a lack of good project management; it is the project manager's fault!
One of the most common problems projects have is an unrealistic timeframe.
Schedule Compression
When do you need Schedule compression ◦
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project planning when the customer requires a completion date that cannot be met, or during project executing when the project manager needs to bring the project back in line with the schedule baseline or to adjust the project for changes.
Schedule Compression – Techniques:
Fast Tracking Crashing
Schedule Compression – Technique: Fast Tracking Doing critical path activities in parallel that were originally planned in series. Issues with Fast Tracking:
Rework, Increases risk Requires more attention to communications.
Schedule Compression – Technique: Fast Tracking
Total Length = 33 Month
Using the network diagram above, what activity would you fast track to shorten the project length? •
•
Activity H could be fast tracked by making it occur at the same time, or in parallel with, activity G. Activities C and H (or any other pair of activities on the critical path) could also be fast tracked by having part of activity C done concurrently with activity H.
Schedule Compression – Technique: Crashing Cost and schedule tradeoffs are analyzed to determine the greatest amount of compression for the least incremental cost. Crashing, by definition, almost always results in increased costs. For example, using the diagram shown in the previous fast tracking discussion, resources could be added to activity G or any other activity on the critical path. These resources could be acquired from activity B or from outside the project.
Schedule Compression – Technique: Crashing
Fast Tracking or Crashing
In crashing or fast tracking, it is best to see all potential choices and then select the choice or choices that have the least impact on the project. If you have negative project float (the estimated completion date is after the desired date) would your first choice be to tell the customer the date could not be met or to ask for more time? ◦
No, the first choice would be to analyze what could be done about it by compressing the schedule.
If you have to choose between crashing and fast tracking, what would you do? ◦
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Adding resources to the project would generally cost more than fast tracking. However, crashing can also mean moving resources around within the project.
If making such moves does not add cost, then crashing would be preferable to fast tracking.
Exercise During project planning, the project duration is estimated to be 33 months. However, you have been given a completion date of 30 months. Using the network diagram below, and the limited information available, describe as many options as possible for shortening the schedule to 30 months. Make any assumptions you need to make in order to come up with as many options as possible.
Total Length = 33 Month
Which of the options listed is the best? To answer the question, think of the impacts to the project of each one. ◦
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Is it option 7? Why not cut quality? Is there another option? Why not do what many project managers do, ask for more resources? But adding resources may also add cost. Why not work overtime? Overtime should be one of the last choices. Most organizations are working at close to 100 percent capacity.Your project working overtime removes the possibility of resources working on emergencies for any other project they are working on, thereby putting other projects at risk. Besides, how much overtime can one take? Overtime is not always free.
Why not do something that does not add cost to your project? The first, and possibly the best, choice is to look at risks. Once it is known the schedule (or budget) must be reduced, a project manager can investigate the activity estimates that contain the most unknowns, eliminate or reduce these "risks" and thus decrease the estimate.
Eliminate risks in the risk management process and everyone wins!
What are the impacts of different schedule shortening options?
Fast track ◦
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Crash ◦
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Almost always adds cost May add management time for the project manager
Reduce scope ◦
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Adds risk May add management time for the project manager
Could save cost and time May negatively impact customer satisfaction
Cut quality ◦
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Could save cost and resources May increase risk Requires good metrics
Crashing and Fast Tracking
Exercise:
1) Imagine that this project has a project float of -3 months. Which activity or activities presented above would you crash to save three months on the project, assuming that the activities listed above represent critical path activities? 2) How much would it cost to crash this project? The options to save three months are:
1) Activities F and H is the least expensive
2) Crashing activities F and H would result in the least added cost, only $5,000.
Exercise Consider: Management has told you to get the project completed two weeks early.What is the BEST thing for you to do? A. Consult the project sponsor B. Crash C. Fast track D. Advise the customer (management) of the impact of the change Did you get fooled by this question? Did you think you had to choose between crashing and fast tracking? There is no information in the first part of this exercise to help you determine which one is better. Therefore, the best choice presented is D, inform the customer of the impact of the change. The exam will ask many such questions requiring you to know that you analyze first and then let management, the sponsor, the customer or other parties know the impact of their requests. A project manager does NOT just say yes! He could say, for example,
"Yes, I would be happy to make the change, BUT the project will be delayed by two weeks, I will need two more resources or the project will cost $25,000 more."
Exercise : Suppose we have a project with only 8 activities as shown in the table. Critical Path is ADEH = 27 Days. Please determine , which activities are the Optimal candidates for crashing. Please calculate A) Cost of crashing for each activity. B) Project cost by duration Slope(cost of crashing) = (crash cost – normal Cost ) / (normal time – crash time )
Project cost by duration
Critical Path is ADEH = 27 Days. Cost of crashing Each Activity
e s i c r e x E
ACTIVITY
PROJECT PROJECT TOTAL COST CRASH COST DURATION 22450
27
A
22700
250
26
A
22950
E
24700
E
26450
23
E
28200
22
H
30200
H
32200
25 1750
2000
24
21 20
e s i c r e x E
Questions, please….
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