Z transformation formula:
Z = T’ – T (cp2)
Where:
T’ = the desired completion time
T = sum of te for critical path activities (i.e. te on the critical path)
cp2 = sum of variances for critical path activities and (cp2) is the square root
Cost and Schedule Variances
The known cumulative planned cost of work performed, the budgeted cost of work performed – BCWP.
The known cumulative actual cost of work performed, the actual cost of work performed – ACWP.
The total planned cost of the scheduled activities, the budgeted cost of work scheduled – BCWS
The schedule variance, SV, (in cost terms): SV = BCWP – BCWS
The cost variance, CV: CV = BCWP – ACWP
Schedule Performance index (SPI) = BCWP/BCWS
Cost Performance index (CPI) = BCWP/ACWP
Estimated Time to Completion = T + (D-TxSPI)/SPI
Estimated Cost to Completion = ACWP + (C – BCWP)/CPI
Capacity Design Capacity: The capacity of a process as it is designed to operate is called its design capacity. It is the theoretical maximum capacity of an operation. Effective capacity = Design capacity - Planned downtime
Achieved capacity = Effective capacity - Avoidable downtime
Total Downtime (Lost Time) = Planned downtime + Avoidable downtime
Achieved capacity = Design Capacity - Total Downtime
Achieved capacity = Design capacity - (Planned downtime + Avoidable downtime)
Machine utilisation = Achieved capacity Design capacity
Efficiency = Achieved capacity Effective capacity
Safety Capacity Average Safety Capacity (%) = 100% - Average Resource Utilisation (%)
Capacity Calculations with Set-up Time Capacity required (Ci) = Setup Time (Si) + [processing time (Pi) x order size (Qi)]
Where:
Ci = capacity requirements in units of time for work order i.
Si = setup or change over time for work order i as a fixed amount that does not vary with volume.
Pi = processing time for each unit of work order i (e.g. hours per part, minutes per transaction, and so on).
Qi = size of order i in numbers of units.
Total capacity required = ∑Ci = ∑[Si + (Pi x Qi)]
