There are two distinct perspectives of workload quantification that greatly influence a schedule. The first is the time-dependant service. For example, cashiers in our grocery store will be at their register at certain times. You would expect the number of cashiers available to grow as the customers come in. This work is time-dependant since the volume of customers walking in fluctuates with a direct dependency on the time of the day and the day of the week.
Best way to illustrate this example is to plan for only one cashier. This cashier will take a certain amount of time for each customer. If the customer volume is low, that cashier can handle the flow of let’s say 2 minutes per customer. So as long as no more than one customer walks in every 2 minutes, there is enough of one cashier. But if there is one customer every minute, then one cashier will not sustain the flow. Each minute, that cashier’s workload increases by 2 minutes because a customer was just added to the line. After 4 minutes, that cashier served 2 customers, and has 2 customers left in line. By the time the cashier takes care of these 2 other customers, another 4 customers are now waiting in line. So the scheduler should be planning for a second cashier during this increase of customer flow. That is a time-dependant work.
The second type of work relates to time-independent tasks. For example, our grocery store needs to stock shelves, clean the floor, etc. This type of task can be accomplished sometime during the day but does not have to happen at a specific time. It is independent of the business volume as to WHEN it will happen. It is not necessarily independent in duration since for example stocking shelves will take longer if you had a particularly busy day with lots of sales. But that task will not matter when you do it in the day (except of course if the shelves are empty…)
Let’s go back to our example and tag each task as to what it is: TD (Time Dependant) or TI (Time Independent)
Cashier:
1.e.i. TD: Service customer at register
2.a.i. TD: Open and close register
Bagger:
1.a.i. TI: Clean entrance
1.b.i. TI: Gather carts from parking lot
1.e.ii. TD: Bag the items
1.f.i. TI: Pick up carts around the exit
Clerk:
1.c.i. TI: Stock shelves
1.c.ii. TD: Service customer on item locations
2.b.ii. TI: Go through shelves inventory
2.c.i. TI: Empty truck
2.c.ii. TI: Store goods in storage room
2.d.i. TI: Stock shelves
Butcher:
1.d.i. TD: Service customer at butcher
1.d.ii. TI: Clean slicer and other bench tools
2.a.ii. TD: Prepare/store meat
2.b.i. TI: Go through meat inventory