Calculations not making sense

[snetzky]

I am running into the usual problem I have with Project in that it
works fine until I start trying to work with resources and it
immediately starts doing stuff I can't explain.


Problem:
I have a Fixed Duration Task with 1 resource at 100% on this task.
The task has a 4 hour duration, which also is the amount of work.
There is a total of 7 of this resource.

All my tasks are fixed duration with the assumption being made that the
contractor will add additional resources if needed.

I am also trying to work with the assumption that a resource will work
on a task until completed.

So if I assign the resource at 100% on this task the resource should be
assigned at 4 hours, right?
4 hour work * 1 unit = 4h duration.

Why then does my duration change to 13.7? If I change my duration back
to 4 hours, Project reduces my resource time to 0 hours.

I have never been able to overcome this problem with Project. It's one
of the reasons many people prefer Primavera or other tools. Primavera
is pricey, but I can at least explain what it's doing when it levels
resources and does the calculations.

Project seems to throw in a bunch of extra calculations but doesn't
explain what they are.

 

[snetzky]

Is part of the problem that I'm expecting Project to treat each task as
a discreet entity until such time as I level?

When doing the calculation of W*U=D what other factors does Project
take into account?

I have all my scheduling and leveling settings to manual, by the way.

 

[Jan De Messemaeker]

Hi,

The formula is W=D*U
I have never seen anything like what you are experiencing.
I try to imagine calendar issues, several resoruces with differnet
alendars...
I'm sur you inroducesd solme curious data because with Fixed duration
normlly this can't happen.
You canb send me the file if you wish.
My address is on my website.
Greetings,

 

[snetzky]

Just realized I had the formula wrong, its W/U =D but that still
doesn't explain why I'm getting the results I'm getting.

Larry

 

[snetzky]

okay..but if Microsoft uses the same math as everyone else:
(dredging up my highschool algebra)
W=D*U
D=W/U
U=W/D

20 hours work=20 hours duration * 1 resource
20 hours duration=20 hours work / 1 resource
1 Resource=20 hours work/20 hours duration

Admittedly with multiple resources it gets more complicated, but there
has to be some other factor that I'm not considering

 

[Jan De Messemaeker]

Hi again,

With multiple resource you can get about any result depending on your data.
Individual asignments are scheduled individually D=W/U doesn't necessarily
hold true on task level.
There are so many combinations that I have to look at the file to propose a
diagnostic.
But be assured, it is your input that provides the result...

HTH

 

[Gary L. Chefetz [MVP]]

I'm not sure what you mean by "There is a total of 7 of this resource" in
the context of the behavior you're trying to describe. Rest assured that
there is an explanation for this. When I setup a task as four hours, fixed
duration, and apply a resource with four hours of availability on the day
the task is scheduled for, the duration stays as defined. What are you doing
differently?

 

[snetzky]

Any recommendations on how to avoid problems with assigning resources
or common gotchas?
I've read Gary's excellent Project tutorial, but something must not
have took.

Larry

 

[Jan De Messemaeker]

Hi,

When you assign only one resource to a task, with a "normal" calendar there
are no Gotchas, everything is as described W=DU.
I still offer to look at your file..

 

[snetzky]

I appreciate the feedback and help. I'll probably shoot you a copy
after work today, Part of the problem may be that I'm not running a
normal calendar and Project may be trying to compensate somehow in a
way that I'm not catching.

In the meantime, I've changed all of my resources to be either on a 12
hour day or 12 hour night shift. Do I need to tell my tasks to use one
or the other, or can I leave them on a 24 hour schedule?

Larry

 

[snetzky]

I appreciate the feedback and help. I'll probably shoot you a copy
after work today, Part of the problem may be that I'm not running a
normal calendar and Project may be trying to compensate somehow in a
way that I'm not catching.

In the meantime, I've changed all of my resources to be either on a 12
hour day or 12 hour night shift. Do I need to tell my tasks to use one
or the other, or can I leave them on a 24 hour schedule?

Larry

 

[Jan De Messemaeker]

Hi Larry,

When there is a resource calendar and no task calendar, teh task's work is
planned using the resouce calendar.
When there are both a resource calendar and a task calendar, work is
scheduled when BOTH show working time
HTH

 

[Steve House [Project MVP]]

There are a bunch of things to keep in mind.
1: Durations are always calculated and stored in minutes. The Calendar
Options "hours per day" entry sets the conversion between the actual minutes
of duration and the number of "days" displayed. So if a task is done by one
resource on each of three shifts so it starts Monday at 8am, is worked on
continuously for 3 shifts, and ends Tuesday at 8am, and the "hours per day"
setting is the default 8 hours, that task is taking place over 24 working
time hours and will display its duration as "3 days."
2: Duration is the number of working time minutes, that is, minutes of the
day when work could legally be scheduled, between when the task begins and
when it ends, regardless of whether work actually will take place during
each minute. When you have more than one resource on the task, the duration
is the time between the earliest starting resource begins and the latest
finishing resource ends. Try this experiment with all settings and calendars
on the out-of-box defaults. Create a 1 day duration task X and 2 resources,
Joe and Bill, with the project starting on a Monday. Assign both resources
to the task. Duration 1 day. Make Monday a non-working day for Bill.
Duration changes to 2 days, task starts Mon 8am and ends Tue at 5pm,
reflecting Joe does his half on Monday and Bill does his on Tuesday. Make
Tues and Wed also non-working days for Bill. Task now starts Mon at 8am and
ends Thur at 5pm but the duration is STILL 2 days because on the calendar
governing Bill's part of the work, those days are not potential working time
and so don't count towards the duration value. Now try it again but instead
of adding non-working days to Bill's calendar, after you add Joe and Bill to
the 1 day task, change Bill's work shift to be swing shift with working
hours of 15:00-19:00 and 20:00-00:00. Now the task begins Mon 8am and ends
Mon at midnight. Now the duration shows 1.75 days, reflecting that the 2
days of total work, 1 day for each resource, overlap (The fact that several
minutes of work might be getting done during each minute on the clock during
the overlap doesn't matter - a working time minute is 1 duration minute
regardless of how many resources are on the job during it.)
3: You absolutly need to group your resources by shift. If I have 3 guys
covering 3 shifts, that should be listed as 3 entries "DayShiftWorker -
100%", "SwingShiftWorker - Max 100%", and "GraveyardWorker - Max 100%" each
with the appropriate resource calendar describing his shift hours and NOT
"Workers - 300%" with a 24-hour calendar. The latter way means that there
are three workers who work together the same hours, a task can use 1 2 or
all 3 of them, their working hours are 24/7 so each of them individually
never takes a day off, never has a lunch break, etc and so even if I only
assign 1 of them, once work on a task begins it will proceed without
interuption until it ends, no matter how long it takes. If Joe is one of
the group and I assign him to a 2 week task, he works without even a single
minute off and doesn't see the light of day or get even the shortest rest
break for 2 solid weeks. (This is why I'm so opposed to using the 24 hour
calendar as the project calendar or for any resources except automated
machinery that really does work like that - humans always get time off and
the calendars that control tasks should always reflect that reality - the 24
hour calendar doesn't allow any time off at all.)
--
Steve House [MVP]
MS Project Trainer & Consultant
Visit http://www.mvps.org/project/faqs.htm for the FAQs

 

[snetzky]

So how do I set a project schedule that reflects that work will be done
in 2 12 hour shifts? Set up a 2 shift schedule taking the breaks of
the two individual 12 hour shifts into account?

For example, my shifts run:

Day Shift
6A-11:30A
12P-6P

Night Shift
6P-11:30P
12A - 6A

so then should my "24 hour" schedule be entered as
12P -11:30P
12 A to 11:30 A

or
6A - 11:30 A
12P - 6P
6P-11:30 P
12 A - 6 A

Or is there another option I'm not thinking about?

thanks for all of your help by the way. Resource leveling is the one
thing that I've never been able to make work in Project. Getting this
figured out will be a definite breakthrough.

Larry

 

[Steve House [Project MVP]]

Pretty close. The calendar shows the hours of work that takes place on a
given workday. You need to have 2 calendars, one for day shift and the
other for night shift. Your day-shift calendar would show 6am-11:30am and
12pm-6pm as you said. The calendar for your night shift is a little more
complicated because a given day of the week will show the MORNING hours for
the shift that began the night before, then the EVENING hours for the shift
that begins that evening. If you have a crew coming in on Monday night at
6pm for the first shift of the week with no one coming to work Sat or Sun
evening, The hours of work on Mon would be 6pm-12am only. Then Tue, Wed
Thur and FRi would show 2 time blocks, 12am-6am and 6pm-12am in that order.
Sat would show one time block only, 12am-6am. (In a 12 hour shift you only
allow your crew 1 30-minute meal period ?!?!?!?! - no offense intended, but
that's positively medieval and is bound to be negatively impacting your
productivity! Give 'em 2 30-minute or 1 60-minute (the two meal breaks
preferrably) and I'll bet your increased productivity will more than offset
the time costs.) Pick whichever of those two calendars descibes the work
pattern of the majority of the tasks and make it your project calendar.
Remember that the project calendar defines the schedule of tasks when they
have not yet had resources assigned or otherwise aren't governed by a
resource calendar. Since tasks only take place when people are there to
work on them and tasks should represent work broken down the the individual
resource or resource team level, I like to see the project calendar describe
the work or a "generic" resource.

If you use the 24 hour calendar and say a task has a duration of 36 hours,
that means it will proceed straight for 36 hours. If it starts Monday at
6am, it ends Tuesday at 6pm. But that's not usually the case - when you
assign that task to a day-shift resource it will start Mon 6am and go for 12
hours. Then he goes home and the task stands down, no work is done on it
until he comes back on Tue. Then he'll work on it 12 hours Tue and again it
stands down overnight. Then he comes in Wed and works 12 hours and it
finally finishes up Wed at 6pm. The reason I like to see perhaps the day
shift calendar as the project calendar is that if I put a task in that has
36 hours duration, I want to see the same work pattern BEFORE and AFTER I
assign the resource - I DON'T want to see the finish initially sitting Tue
at 6pm before I assign the resource and then have it jump to Wed at 6pm
after - I want to see the same hours before and after. Now if I initially
put it in and shows day-shift hours starting Mon 6am and finishing Wed at
6pm but then I assign it to a night shift resource, it'll jump to start Mon
at 6pm and end Thur at 6am but the cumulative effect of that sort of change
won't affect the total elapsed time of the project by a signifigant amount
while the other way, using the 24 hour calendar as the project calendar, can
lead to a dramatic difference in the total elapsed time in the project
schedule between before resources are assigned versus after.

HTH]

 

[snetzky]

The working schedule isn't my choice, but there are a couple of 15
minute breaks in there too, I just didn't put them in.

The schedule is 24 hours 7 days a week, so I think I'm okay on that
point. The other question I have is that if a task is going to
continue with the night shift taking over where the day shift left off
or vice versa, do I assign both a day and night shift resource to the
task and figure that Project will figure out where to assign the
resources?

Most of the tasks I'm working with won't benefit from additional
resources being added (1 crew is about all that can work on a task at
one time).

Thanks again for all of your help. I think the calendars is the
majority of the problems I'm having.

Larry

 

[Steve House [Project MVP]]

Before you commit yourself to using the 24/7 calendar as the project
calendar think it through a bit to make sure it really should apply in your
case. The project calendar is not the overall hours of business of your
firm or organization. Rather, it's the hours of the day when typical tasks
TAKEN AS DISCRETE BLOCKS OF WORK are likely to be or will need to be
scheduled. If my typical task is something where one crew works on it
during the day and another crew takes over for the night shift, the task
running continuously day and night with different crews alternating on each
shift until it is done, then the 24/7 calendar may indeed be appropriate.
But if the task might be assigned to a day shift resource OR might be
assigned to a night shift resource but will only be worked on by that one
resource or crew from its start until its finish, work being interrupted
during the resource's off-duty hours, then whichever way work is assigned it
will only take place 12 hours a day and the 24 hour calendar will NOT be an
accurate description of the way work will actually proceed.

I don't know where you're located but I'm surprised your company can get
away with that break pattern. Where I last had to look into it, admittedly
quite a fair number of years ago so the laws may have changed since then,
the statutory minimums were that in an 8-hour day, workers were required to
get at least a30-minute unpaid lunch and 2 10-minute paid breaks (10 was the
minimum required by law, most firms did 15). Over 8 and up to 10
consecutive hours added a 3rd 10-minute paid break while over 10 and up to
12 mandated the extra 10-minute break be changed into a 30-minute PAID meal
break. If the day ran over 8 hours but less than 10, all hours over 8 were
at time-and-a-half. Over 10 but under 12, all hours over 8 went to double
time. Over 12 consecutive working hours were absolutely prohibited under any
circumstances except for public safety and emergency workers such as police
and fire and there was an absolute minimum of 8 off hours between any two
consecutive work periods (which sometimes made for some interesting days off
juggling for workers who moved from one shift to another). Workers could
not be scheduled for more than I think it was 6 working days in succession
and there had to be at least 1 day off before starting the next work week.
Only under very unusual circumstances could a worker be scheduled for more
than 44 hours astheir normal work week and mandatory overtime kicked in at
44 hours regardless of how long each workday was.

 

[snetzky]

I think the 24 hour schedule is on target then, as most of my tasks
will be worked until they are done. To show that, do I need to assign
both a day and night crew to the task and let Project figure out how to
allocate it?

I think the discussion of working hours and breaks is probably OT at
this point, as I have no power to change it, since I was hired as a
scheduler rather than as a project manager.

The main thing I need to figure out is how to get Project to tell me
whether or not I have enough people to get the work done in the three
weeks I have to get it done.

Larry

 

[Steve House [Project MVP]]

LOL - the break discussion is more academic rambling than anything else, I
admit. I find there's a regressive tendency generally in businesses today,
many of them rolling their practices and policies back to those of the bad
old days. I think that is going to ultimately prove to be a case of it
shortsightedly shooting itself in the foot in the long run and I have a
tendency to philosophize against it when the opportunity arises. Didn't
mean to drift too far off topic.

I'm not sure what you mean by "let Poject figure out how to allocate it."
Project never figures out allocations, that's up to you. It's role there is
to show you the results of varous experiments you might try with different
allocations, a calculator for you to use in a what-if set of trials. to see
what allocation will best achieve your goals. "Resource" is a project plan
is a skill set as well as an individual. A "Task" is a specific observable
and measureable activity done by a resource. The tasks need to broken down
and detailed to the level of describing the work done by the individual
resources viewed as skill sets. If your task is something that involves,
lets say, engineers, plumbers, accountants, carpenters and nurses, those
wildly different skills means there's a good chance the task needs to be
further broken down into the specific activity done by each. In your
resources you wouldn't have one big group - you'd either have individuals
listed by name or grouped together into groups with the same skills, the
maximum allocation indicating the number of individuals in each group - so
Engineers (500%) would be one group consisting of 5 engineers whom you've
elected not to detail out by individual name. Where's this going? When you
set up your resource for your project, you should have resources listed
either by indivudal worker's name OR by skill group. Further, since you're
in a multi-shift environment, you need to indicate WHO is on WHAT shift - so
you'll have perhaps a group "DayShiftWelders (500%)" and another
"NightShiftWelders (700%)" indicating 5 welders working days and 7 welders
working nights. Each group has a resource calendar asociated with it that
descibes its hours of work. You have a task, say "Weld 100 girders to
footplates," that can start Mon 8am and you expect it will require 350
man-hours of work to complete. Now you can assign 2 days shift and 3 night
shift or 3 day shift and 5 night shift or all the dayshift and none of the
night shift or .... and in each case Project can tell you when the task will
likely finish. But it's always up to you to tell project how many people to
put on in what shift, it won't figure it out for you. You try one
allocation experiment and if it works to meet your goals, fine. If it
doesn't, you try a different allocation until you come up with one that
works.

 

[snetzky]

I'm in agreement about the regressive thing, but I gotta make a living.
<grin>

Bottom line is, I don't have time to do this at the granularity you
suggest, nor do I see it as being particularly useful, given the
structure of the project. As the majority of the tasks don't fit into
a particular task network, they just have to be done sometime between
the start and end of the project, I'm inclined to identify priorities,
which cranes (probably the most critical resource) are needed, and then
let the supervisors on the floor figure out the people resources and
which jobs to work on. The biggest thing here is whether or not they
are getting all of the work done and can finish it all by the deadline.

I have to admit, Project was not my first choice, and this experience
hasn't changed my mind any.

Larry