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Baseline Schedule

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Jaco Stadler
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I was wondering what is used in the planning industry (And other parts of the world) for the baseline schedule.

1) Optimistic
2) Pessimistic
3) Most Probable

My experience to date I have found that.

Most Construction Planners Plan Optimistic.

Most EPC Planners Plan Pessimistic.

1) I was wondering why such a variance maybe somebody out their know ???

2)Is it correct to make such a statement.

Replies

Daya Sugunasingha
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If you are too pessimistic at Tender Stage you may not win the contract?
If you are too optimistic during the Contract Stage you may not complete on time?
DS
Joseph Erwin Carg...
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Hello guys,

I just want to share most of my experience when doing schedule, and that is most of he time I am being pessimistic, and somtimes i cant do anything but to follow if what are being laid on the contract..but i just make sure that everytime ive come up with a constraint schedule i always talk to the superiors and insist that the given time for the project is not enough....just keep on planning guys..
Philip Jonker
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Pessimistic or most practicable
Philip Jonker
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Hi guys,

This lpgin took me five minutes, however I think we are talking the truth
Charleston-Joseph...
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I cant imagine the effort of generating such schedules with 35,000 actitivities for one projects. The effective way, maybe, is to present schedule to the client for approval without discussing optimistic, pessimistic or most probable dates. The dates should show only attainment of contractual dates Upon approval,the schedule is the contract schedule. All project activities and performance will be compared to the contract schedule. The contract schedule is the baseline schedule without any thoughts that such schedule is optimistic, pessimistic or most probable.
Stuart Atkinson
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Specifically to Joanne Foster.

BIGGER GRIN

How true you are.
DATTATREYA PADHARTHI
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effectivness of Schedule risk planning is proportional to the detailing of the schedule.
First Schedule/Cost Risk Analysis (Monte-Carlo simulations) is an effective way of finding out prob of the job completion on a date or so.
To make sure of time/productivity estimates, say for eg 150-200 activities (proposal stage), with proper logic/durations/distributions, find out the most sensitive activities (top 10%), attack them, try to narrow down their spreads & so on and so forth. In this way try to get an optimal solution (which in practice is like a mirage).
Now "relationships", FS, FF, SS all are used at some point of time because of nature of activities & also level of details available (Civil/Strl works are quite easy compared to Piping works). These lags also have their own duration distributions. So this increases the degree of freedom.

In Strict sense unless you have FS relationship, it is not feasible to get a good solution using risks. FS relation means too much details (Is that level worth in a schedule???).
Pertmaster, Crystal Ball & all risk analysis s/wares are effective to the limit of understanding of the scheduler. It is the inputs given to S/ware which governs the solution & this inturn depends on the planner’s understanding of job & its dependencies.
Finally, experience/knowledge of the job is the key to any solution. S/ware expedites the solution.
Regards
Dattatreya




Philip Jonker
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Hi Jaco,

I think by now you understand how I think. I do not believe this story about pessimistic/optimistic planners has any foundation. Probably another funny survey. In real terms it is the planners job to provide a realistics schedule. OK it is questionable about how many real planners are around. But any client planner who can come up with realistic dates, other than a thumbsuck, I still have to find. The intermediates, ie managing contractor planners or EPC etc, have a vague idea. so the aforegoing two types work out durations. As a result the construction planners have to work within the bounds of what the previous two animals decided. He then comes up with a practical schedule which can either reflect that the time allowed is too short or too long. If is too short he works out how the end dates can be met, by adding resources, and cutting durations to the bone which is the case in most instances, hence the optimistic view. If the duration is too long, he simply stretches the schedule, has a smile, and meets the end date (not often the case). The question is where does the problem come from. Defintely not caused by the construction planners, and I have a lot of sympathy with them

Groete

Philip
Joanne Foster
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here’s my 2 cents...

Complete 3 point estimating
optimistic is based on the most probable best time eg driving to work and getting all green lights
most likely is based on the most probably time eg driving to work and getting some red and some gree lights
pessimistic is based on the most probable worst time eg driving to work and getting all red lights.

Now...the event of getting a flat type is a risk and entered into our risk register, because it has less than 50% chance of occuring.

When it comes to the schedule, we start with most likely estimates, we apply the PERT forumala to the critical path (and near to critical path) activities and update those durations to include some ’schedule risk’ into the critical path.

We also baseline rework into the schedule...so in the software section you would see req’s analysis > prelim des > detailed design > code & unit test - c&ut rework - dt&e rework

right wrong or indifferent...it doesn’t really matter, because before the ink has dried on the contract the schedule changes *grin*
Daya Sugunasingha
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I suspect that Jaco Stadler is most probably correct that most planners plan pessimistically as their base line at the outset of a project plan because of all the unforseen risks of the future.
I usually find that at competative tender stage the mind set is to be optamistic in order to win the contract.
When the won contract however arrives on the project planners desk the mind set changes to pessimistic or realistic with a little bunce for some of the risks ahead on his overall programme.
On the short term programme he would opt for the most optamistic method and durations within the bounds of the cost constraints.

How long does it take? Well! this begs another?
It all depends on the cost and resourses available.
Method of putting together of the project will depend on the above. For example you may be able to use large machines and prefabricate and save a lot of time if cost and resourses and site/project boundaries allow.
How long is a piece of string? it depends!
Usual wording:
How long does it usually takes?
Then: what will be your estimate if everything will go smoothly - without rains and interruptions?
Then: and what is your longest estimate - if the risks that may be happen (rains, interruptions and other troubles) will really occur at the time the work is performed.
Besides events you may estimate resource productivity (skills) - if the resources will have best productivity, usual productivity and worst productivity.
You shall also estimate probable risk events like failures in electicity supplies or rework. These events may take place in pessimistic scenario.
You will have three schedules that may contain different events (rework only in pessimistic schedule). Comparing finish dates you will notice that optimistic date is closer to most probable than pessimistic.

Vladimir

www.spiderproject.ru/index_e.htm
Jaco Stadler
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If I read the thread 17 Jul 2004 at 22:16 - Risk analysis Vladimir Liber this it tells me three schedules will be calculated. (Is this incorrect)

But I don’t think that is the question.

When you ask some Planners how long something takes he tends to answer you the direct duration only. (Example 8 Days)(He think 80 hrs without any interruption

Other planners you ask the same question he says 12 Days when asked why he says what about if it Rains or you have labour problems etc. (Risk) (He thinks 80 hrs with disruptions)

So maybe I should have used different wording in my question. Will do next time
No, Jaco.
Optimistic schedule is calculated basing on optimistic duration and cost estimates and certain events.
Most probable is based on most probable estimates and risk events that have probabilities exceeding 50%.
Pessimistic schedule is calculated basing on pessimistic estimates and all probable risk events.
Probability curve will have maximum at the most probable schedule results but it is asimmetrical. So if you want to calculate which target dates and costs will have 50% probability then these dates and costs usually will be between most probable and pessimistic.
In Demo version of Spider Project that may be downloaded from http://www.spiderproject.ru/spider_e.php you may find an example of the probability calculations for the sample project including trend analysis. Check it.

Regards,
Vladimir

http://www.spiderproject.ru/index_e.htm
Jaco Stadler
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Three schedules are calculated. As the result we receive optimistic, most probable and pessimistic estimates of project duration and cost.



Actually there is not such thing as a baseline schedule if risk management approach is involved.
There are target dates and target costs for the whole project and major milestones. They may be established different ways.
1. Project Planner creates optimistic, most probable and pessimistic schedules. Then desired probability of meeting target dates and costs is determined and desired dates and costs of the project and major milestone are calculated. These dates are used in the contract negotiations. When target dates and costs are proposed project planner calculates probabilities of these targets achievement. If they are satisfactory then the contract may be signed and these target dates and costs determine what is used for performance estimating (baseline though not schedule). During project performance project planner estimates what is happening with the probabilities to meet targets and suggests correstive actions when success probability trends are negative.

2. When target dates and costs are determined initially then project planner solves another task. What resources are necessary to perform the project on time and within budget with the reasonable probability. If this is impossible then project planner shall inform project manager about dates and costs that are real. If the probable project results will be known ASAP then project manager has more chances to defend reasonable project schedule and budget changes.

Usually most probable schedule has low probability of success (around 30%) and thus should not be used as a baseline.

Vladimir

www.spiderproject.ru/index_e.htm
Stuart Ness
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Actually, Jaco, on second thoughts, even accuracy is non-existent in planning; at least in the construction industry!

In the construction industry, the planner is given a pre-determined contract period, with a pre-determined start date and a pre-determined completion date. A few (already established) “Milestone” dates will be dispersed throughout the programme like confetti, which are already likely to determine the extent of the engineering phase, the construction phase and the commissioning time.
A couple of weeks for mobilisation is tossed in for good measure, and a touch of “realism” is shown by adding something for procurement and shipping materials and equipment.

The great thing is – the baseline or Contract Schedule does not reflect reality!! Contract durations are driven by the commercial needs of Clients and Employers, irrespective of factors such as weather, long leads on materials and availability of resources. All you have to do as a planner is to join up the dots!! In fact you are no longer a planner – you are just a monitor!

Maybe that explains the difference that you have noted between an optimistic planner and a pessimistic one!

Stuart

www.rosmartin.com
Stuart Ness
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Mmmmmm.....whatever happened to accuracy?

Cheers,
Stuart

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