J
Jan M.
Hi,
I've been experiencing some problem with MS Project calculation of earned
value. For certain tasks of my project, there was a discrepency between BCWP
as shown in the earned value table and BCWP in the timescale. Whenever I
exported data to Excel to graph CPI and SPI, values in the graph didn't match
the values of the earned value table, which is quite annoying.
I thought the problem was due to my using of physical % completed to
calculate earned value. It took me some time to realize that the problem was
caused by the tasks to which I had applied a work contour! So I made a very
simple project to look further into that. Here are the results of my
simulation:
Project description:
1 task
40 hours of work
1 ressource at 1$/h assigned to the task at 100%
Calendar 8h/day, 5 days/week
Work contour applied: Back loaded
Duration as calculated by MS Project: 8.33d
Earned value method of calculation: % complete.
After saving the baseline, I applied the task usage view and inserted the
columns "% complete", "% work complete" and "physical % complete". What I
first noticed is that all "% fields" are tasks fields but only "% work
complete" is an assignment field (Thanks to Julie S. for the hint!).
I entered 4 hours of actual work on the first day(status date on the same
day): % complete as calculated by MS Project is 13%. On the assignment line,
BCWP reads 4$ (table and timesheet), but on the task line, BCWP reads only
0.93$ (table and timesheet). Which means that MS Project uses % work complete
to calculate earned value for assignments instead of % complete as it does
for tasks. The only reason I can come up with to explain 0.93$ of earned
value out of 40$ with 13% complete, is the distribution of work that is
skewed to the right due to the work contour. Having completed 10% of the
work, I would have prefered BCWP to be 4$ as shown on the assignment line.
Then, I made another simulation: I changed the earned value method of
calculation to physical % complete and copied % work complete (10%) in
physical % complete. As with % complete, BCWP reads 4$ on the assignment line
( table and timesheet). But now, BCWP reads 4$ on the task line in the table
and 0.67$ in the timesheet.
So, the discrepency I experienced in the above mentionned project was caused
by my using of work contour with physical % complete. To make sure I was
right, I made a simulation the same simulation without any work contour:
1) % complete as a method of calculation: BCWP is 4$ on the assignment line
(table and timesheet) and 7.27$ on the task line (table and timesheet). The
difference is "normal" since MS Project uses % work complete for BCWP
assignment and % complete for BCWP task. At least there is no discrepency
between earned value table and timesheet: values exported to Excel will match
the table in MS Project.
2) physical % complete as a method of calculation: BCWP is 4$ everywhere.
My recommendations:
1)Unless someone can prove me I got it all wrong, I advise against using
work contour for projects as far as earned value is concerned: earned value
calculation is biased by work contour.
2)I strongly suggest that Microsoft provides a method for calculating earned
value based on % work complete:value is earned as work is accomplished, not
as time passes by.
3)The same method of calculation should be used for assignments and tasks.
Thanks for going through all this.
Any comment someone?
Jan M.
I've been experiencing some problem with MS Project calculation of earned
value. For certain tasks of my project, there was a discrepency between BCWP
as shown in the earned value table and BCWP in the timescale. Whenever I
exported data to Excel to graph CPI and SPI, values in the graph didn't match
the values of the earned value table, which is quite annoying.
I thought the problem was due to my using of physical % completed to
calculate earned value. It took me some time to realize that the problem was
caused by the tasks to which I had applied a work contour! So I made a very
simple project to look further into that. Here are the results of my
simulation:
Project description:
1 task
40 hours of work
1 ressource at 1$/h assigned to the task at 100%
Calendar 8h/day, 5 days/week
Work contour applied: Back loaded
Duration as calculated by MS Project: 8.33d
Earned value method of calculation: % complete.
After saving the baseline, I applied the task usage view and inserted the
columns "% complete", "% work complete" and "physical % complete". What I
first noticed is that all "% fields" are tasks fields but only "% work
complete" is an assignment field (Thanks to Julie S. for the hint!).
I entered 4 hours of actual work on the first day(status date on the same
day): % complete as calculated by MS Project is 13%. On the assignment line,
BCWP reads 4$ (table and timesheet), but on the task line, BCWP reads only
0.93$ (table and timesheet). Which means that MS Project uses % work complete
to calculate earned value for assignments instead of % complete as it does
for tasks. The only reason I can come up with to explain 0.93$ of earned
value out of 40$ with 13% complete, is the distribution of work that is
skewed to the right due to the work contour. Having completed 10% of the
work, I would have prefered BCWP to be 4$ as shown on the assignment line.
Then, I made another simulation: I changed the earned value method of
calculation to physical % complete and copied % work complete (10%) in
physical % complete. As with % complete, BCWP reads 4$ on the assignment line
( table and timesheet). But now, BCWP reads 4$ on the task line in the table
and 0.67$ in the timesheet.
So, the discrepency I experienced in the above mentionned project was caused
by my using of work contour with physical % complete. To make sure I was
right, I made a simulation the same simulation without any work contour:
1) % complete as a method of calculation: BCWP is 4$ on the assignment line
(table and timesheet) and 7.27$ on the task line (table and timesheet). The
difference is "normal" since MS Project uses % work complete for BCWP
assignment and % complete for BCWP task. At least there is no discrepency
between earned value table and timesheet: values exported to Excel will match
the table in MS Project.
2) physical % complete as a method of calculation: BCWP is 4$ everywhere.
My recommendations:
1)Unless someone can prove me I got it all wrong, I advise against using
work contour for projects as far as earned value is concerned: earned value
calculation is biased by work contour.
2)I strongly suggest that Microsoft provides a method for calculating earned
value based on % work complete:value is earned as work is accomplished, not
as time passes by.
3)The same method of calculation should be used for assignments and tasks.
Thanks for going through all this.
Any comment someone?
Jan M.