Sometimes a parametric formula for labor is not used to calculate the effort for a single resource group, but for a set of resource groups with different cost rates. For example the formula "program_mgt = 9% of total effort" might apply to everyone in the program management office combined including the project managers, project admins, project finance, scheduling and program directors. There are two ways to accommodate this:

• The recommended way is to determine up front how your effort is going to be split between the various resources within the program management group, for example the program mgt. effort might split 50% to the project managers, 10% each to admins, finance and scheduling and 20% to program directors. In this case instead of one formula, create 3 or 5 formula up-front, as follows:
  • project_manager_effort = total_effort x program_management_percent x 0.5
  • admin/finance/scheduling_effort = total_effort x program_management_percent x 0.1
  • program_director_effort = total_effort x program_management_percent x 0.2
  • If you prefer to adjust the splits locally within your estimate then you can use a single formula with a resource-specific parameter called "split_percent" and maintain the 0.5, 0.1, 0.2 allocation % within each formula
  • Be sure that the splits add up to 100%
• The alternative way is to create one formula for program_management_effort, against a dummy resource which is not costed or has a zero rate. Then create a second, co-dependent, formula using a base parameter which refers to the program_management_effort resource, multiplied by the split percentage for each PMO resource
  • In this case, since the same (second) formula is used for the actual PMO resources, the split percentage should be a parameter. This only works if you wish to determine the split %'s locally within your estimate as a resource-specific parameter
  • Bear in mind that the formula rank for the second formula must be higher than the rank for the program_management_effort formula, so that two formulae are calculated in the right order.