AAOM Handbook

INTERNAL USE ONLY

Step 3: Special Causes To calibrate for special causes probability of the events and impact on performance must be considered and multiplied through by the unconstrained column of each process in the Business Structure. This maintains the shape of the distribution by generating variability close to the actual variability of the process. There are instances where the calibration impact hasbeen applied to the constrained output column. This does not result in a significantly different calibrated output based on random probabilities. Figure 15 to 17 provide example tables for including zero days, days below LCL and days above UCL.

Probability

Impact/Calibration

Total zero days

24

0 0 0 1

1 1 1

Total days Probability

366

0.06557377

0

Figure 15 – Example table to include zero days

LCL

9951 Max

Ave

Min

Probability

Calibration

Days below LCL

25

9922.932

4183.813633

208.08

1 0 0 0

0.19

Total days Probability

366

1 1 1

0.068306011 Min (adj)

Most likely

Max (adj)

0.997179379

0.420441527

0.020910461

Figure 16 – Example table to include days below LCL

UCL

60276 Max

Ave

Min

Probability

Calibration

Days above UCL

49

125265

77903

60296

0 0 1 0

1 1

Total days Probability

365

0.134246575 Max (adj)

Most likely

Min (adj)

1.85 1.00

2.078

1.292

1.000

Figure 17 – Example table to include days above UCL

Step 4: Modelling the ‘Constrained’ Output to the valuable mineral: There is a well-established logic to calculate the constrained process output volumes. The logic is dependent on whether the is first, intermediate or last in the value stream. The constrained output column takes into consideration the rate of the upstream processes, the capability of the downstream processes, the level of the stockpile upstream, the level of the stockpile downstream and the system constraint. The logic uses variables defined below. • Unconstrained - Unconstrained rate, i.e. the production rate of a process generated statistically to represent stable and representative operating level with independent variation. This would refer to the unconstrained column depicted in Figure 16 above. • System Constraint - System Constraint, i.e. the minimum of the unconstrained rates of all the productive units or processes in the Business Structure. It is recommended that the accountable person creates an additional column for the System Constraint where it returns the minimum which can then be referenced when creating the constrained rate output.

Operational Planning: Building a Business Structure Performance Model Page 18 of 39