Conditions of a Subtask
A task should be broken into subtasks if any of the three conditions below apply:
•The task can be performed in more than one way, each involving a method or procedure that is significantly different from the other(s).
•Performance of the task under different conditions require substantially different steps, methods, skill or knowledge.
•The task is so complex that each "step" or element is actually a task in itself.
When a task is broken into subtasks, the original (parent) task simply becomes an "organizer" of the subtasks.
When you break a task into subtasks, watch for "decision tasks." For example, if there are two methods of performing a task, do you need a task for selecting which method to use?
Position of Subtasks in the Job Analysis Hierarchy
What "Significantly Different" Means
How different does it have to be, in order to break the task into subtasks? If one or two steps are different, and the rest are the same, there is probably no need for subtasks. The alternative steps can be pointed out within the list of steps for the task.
If quite a few of the steps are different, say close to half, it is usually better to break the task into subtasks.
Example "Organizer"
This illustration shows a task being broken into subtasks. Notice that the original parent task becomes an organizer of the two subtasks. When you count the tasks in your list, the example situation would count as two tasks, not three. The organizer is not relevant.
Examples: Three Types of Subtasks
Subtasks Based on Different Methods or Procedures
Here is an example of a procedural task:
•"Load the ADV program..."
The analyst determined that the program is normally loaded using an "auto boot" routine. Sometimes however, the auto boot routine fails. In this case, the program must be loaded "manually." The manual procedure involves very different steps, displays and so on.
As a result of discovering the existence of two alternative methods of loading the program, the analyst breaks the task into two subtasks:
•Load the ADV program using the auto boot routine.
•Load the ADV program manually
Subtasks Based on Different Conditions
This is the original task:
•"Plan a convoy formation."
This task, which involves the organization of military vehicles in a convoy, is normally done on domestic highways to move vehicles, personnel and goods from one base location to another. The analyst asked the Subject Matter Expert (SME) if the convoy organization might vary in different conditions. "Of course!" the subject matter expert said. "It's entirely different if we"re in combat."
The analyst decided then, to break the task like so:
•Plan a convoy formation for civilian, peaceful conditions.
•Plan a convoy formation for military, combat conditions.
Subtasks Derived From a Large, Complex Task
The original task:
•"Disassemble a ... turbine in preparation of overhaul"
This turned out to be a big turbine, such as those used in electric power plants. Disassembly took days, not hours. The project went though various stages, each having significant steps. It turned out that this task involved a list of subtasks.
•Remove a .... turbine housing.
•Remove turbine blades
•etc.
