Project Scheduling Tools

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 1. Sequencing

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

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

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

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

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

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

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.

Finding Random Variates, Problem 2.1 BCPMF CDF Mean – Mean Mean Mean Random probability of.28 gives B random variate of 1;.46 gives C value of 3.

Simulation of Problem 2.1 RN B(2) RN C(3)LengthPath ACD ABD ACD ACD ACD Expected length = 5.8> 5 (merge event bias) Criticality index of ACD = 0.8 or 80%

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

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