What is the major difference between Fixed Work task and Fixed Unit task?

Have you ever wonder what is the major difference betweent the two type of tasks? Here is a Powerpoint presentation to show the difference.

Here is a quick summary:


Examples of a Fixed Work Task

Based on normal situation, each clerk can prepare 1 document per hour. She can prepare 8 documents per day. If there are 4 persons to work on different documents, there will be a total of 32 documents to be prepared within 1 day. In this case, if our task is to process 32 documents, they can only be completed within 32 man-hours (fixed work effort needed). So, to complete this task, we can assign 4 clerks to prepare 8 documents in one day, or 2 clerks to prepare 16 documents in one day.


Examples of a Fixed Unit Task

If one clerk will only work 8 hours a day (assuming each resource is one unit. Each unit will contribute 8 hours per day), no matter how urgent is the work. If our task is to supply 2 clerks to process the documents for 2 days without considering the urgency of the documents, so for this task, each clerk will work 8 hours in one day and 16 hours in 2 days. Based on our statistics (or estimation), 16 documents should be produced for each clerk. So, we can process 32 documents within 2 days with 2 clerks assigned to the task.