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Project Scheduling Tools

Project Scheduling Tools. 1. Sequencing. There are four possible sequencing modes in MS Project. Suppose B follows A. FS: Finish Start – Start B after A is completed SS: Start Start – Start A and B at same time

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Project Scheduling Tools

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  1. Project Scheduling Tools

  2. 1. Sequencing • There are four possible sequencing modes in MS Project. Suppose B follows A. • FS: Finish Start – Start B after A is completed • SS: Start Start – Start A and B at same time • FF: Finish Finish – Finish A and B at same time • SF: Start Finish – Start A after B is completed • Lags are delays between work on activities

  3. B FS Sequence - Traditional A E.g. Sand and Paint A Lag B E.g. Sprinklers and Landscape

  4. SS Sequence B A E.g. Plant Lawn and Flowers A E.g. Drywall: Hang and Tape Lag B

  5. FF Sequence B A E.g. Olympics A Lag E.g. Olympics B

  6. SF Sequence B A E.g. Not Practical A B E.g. Ocean Cruise Lag

  7. 2. Activity Uncertainty • PERT assumptions (Richard Schonberger and Ken Mac Crimmon) • Beta distribution assumption • PERT approximation formula for mean and variance • Estimates of a, m, and b • Errors of above up to 30%, but tend to cancel • Worse problem is merge event bias (probability near-critical path becomes critical) – estimates consistently optimistic

  8. Example 2.1 B,2 A,1 D,1 C,3 Critical path is ACD but ABD is near critical. Criticality index: probability path critical.

  9. Use Simulation or Monte Carlo Analysis • Generate random numbers (electronic, formulas, tables, books) i.e. 28 • Convert to random probabilities i.e. .28 What is probability of probability? • Convert random probability to random variate. Follows distribution of say actual activity time.

  10. Finding Random Variates, Problem 2.1 BCPMFCDF Mean – 1 1 2 .3 .3 Mean 2 3 .4 .7 Mean + 1 3 4 .2 .9 Mean + 2 4 5 .1 1.0 Random probability of .28 gives B random variate of 1; .46 gives C value of 3.

  11. Simulation of Problem 2.1 RNB(2)RNC(3)LengthPath .28 1 .46 3 5 ACD .97 4 .09 2 6 ABD .63 2 .33 3 5 ACD .53 2 .76 4 6 ACD .73 3 .00 5 7 ACD Expected length = 5.8 > 5 (merge event bias) Criticality index of ACD = 0.8 or 80%

  12. Project Simulation • Simulation includes • GERT – Graphical Evaluation and Review Technique • Crystal Ball – Copy comes with text • Simulation includes • Probabilistic branching from node – B may follow A • Probabilistic times for activities – various distributions • Flexibility in node realization – activity time can = 0 • Looping permitted – rework • Critique of Simulation – R. Schonberger recommends intensive critical path scrutiny

  13. 3. Limited Resource Scheduling • Resources include labor, material, equipment, space, and money • Money versus time tradeoffs • Methods • Crashing – How to shorten activities – cost penalties • Resource loading – amount of resource needed per period. • Resource leveling or balancing – evening out resource use, reacting to limited resources • Simulation programs can help level

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