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

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

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

6. SF Sequence A
E.g. Not Practical B 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 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
B C PMF CDF
Mean –
Mean
Mean
Mean
Random probability of .28 gives B random variate of 1; .46 gives C value of 3.

11. Simulation of Problem 2.1 RN B(2) RN C(3) Length Path
ACD
ABD
ACD
ACD
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
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