Hi,
I got a message from one of my Blog readers. Here it is
“Dear Sir,
I got confused in this topic.
according to Effort Driven definition, to have a “constant Work value”, there would be compensation between Duration and Unit when one of them changes. which means(my idea) to keep Work value fixed, when Duration(Unit) changes, Unit(Duration) will change automatically. Now the question is: when I create a task which is Effort Driven, I also select the task type as fixed Duration. Now when I change units, I will have changes in Work value(as it is fixed Duration) which has contradiction with the Effort Driven definition which says “Constant Work value”
I do appreciate if you clarify the issue.”
OK. What does Effort Driven mean? It means MORE HAND LESS WORK!
The Relation between Units, Duration and Task is: DURATION * UNITS = WORK
So, of course, if I have a fixed duration, and when I change Units, the work will be changed! If you want to have fixed hours (work), than you should mark your Task as Fixed work. Let me show you that:
OK! Now I will choose this:

and then click:
Now I am going to add two resources:
And I will assign John to the Task!
You can see there is work = 24 hours, and Units = 100%
I will change, for instance, units from 100% to 50%
and I will get:
and you can see, that Duration is changed, according to the formula: DURATION * UNITS = WORK, e.g. Duration * Units 50% (4 hours per day) = 24 hours Fixed work –> Duration = 24/4 = 6 days!
So, my dear Blog Reader If you want to make work as a constant choose Fixed work for the Task, or Tasks
Now the announcement for my next Post. If I change Duration from 3 days to 5 days you will get:
I will get:
Work, and Units are unchanged, and that SEEMS LIKE A BUG, BUT IT IS NOT! Read my next post for that!
Back to effort and non effort driven Tasks:
When you Fixe work Task, it is always Effort driven!
Now I will assign Mary to the Task:
As you can see, I still need 24 hours of Work for the Task, but since I have Mary on board, both John and Mary will spent less hours on this Task. And that is what effort driven means. And you can see effects of Effort Driven Task when you add or remove a resource/resources to/from Tasks.
I hope that my blog reader will find this Post useful!
For some more examples read this:
https://ntrajkovski.wordpress.com/2011/11/21/task-types-and-how-they-affect-the-schedulepart-1/
https://ntrajkovski.wordpress.com/2011/11/24/task-types-and-how-they-affect-the-schedulepart-2/
https://ntrajkovski.wordpress.com/2011/11/28/task-types-and-how-they-affect-the-schedulepart-3/
https://ntrajkovski.wordpress.com/2011/12/01/task-types-and-how-they-affect-the-schedulepart-4/
Regards!