It is essential to understand that duration and work are not the same
measure. Duration measures time but work measures sweat. That is why I
always try to refer to duration by "hours" but work by its proper unit
"man-hours." If you had 1 man working full speed for 1 day, you have 1
man-day of work. If you have 1 man working full speed for 10 days, you have
10 man-days of work. BUT, if you have 10 men working full speed for 1 day
you ALSO have 10 man-days of work. Work measures the total useful output
you're getting and duration measures how long it takes to get it.
The units is a percentage that reflects how much of the duration is getting
translated into useful work output and so indicates the rate that work is
getting done. The Prime Directive is Work=Duration*Units. If I work 8
hours duration at 100% units, I do 8 man-hours of work. But if I do 8 hours
of duration at 50% units, I only do 4 man-hours of work. Maybe I'm talking
with my buddy and not working at full speed. Or maybe I'm juggling two
things at once and can't really devote full attention to either of them and
as a result each of them takes me longer to complete than if I was working
on just that one thing. If I have 1 person doing 10 days duration (80
hours) at 2% units, he does 80*.02 or 1.6 man-hours of work, spread out over
the 10 days of working time. In other words it has taken him 10 days to
achieve what WOULD have only taken an hour and a half if he had devoted his
full attention to it. 11 people working 48 hours duration at 2% units each
is 48 * .02 * 11 or 10.56 man-hours of work - the team is taking over a week
to accomplish what should have taken them only an hour if they had got their
act together and pulled together as a team to get 'er done ASAP.
--
Steve House [MVP]
MS Project Trainer & Consultant
Visit
http://www.mvps.org/project/faqs.htm for the FAQs
