How is actual duration calculated at the project summary level?

J

Jweaver

I have a project with the following information. The actual duration on the
project summary line seems awfully low, which I believe may be driving the
low overall percent complete. But I don't know which field is driving the
calculation. Looking at the individual tasks, the actual duration should be
around 20 days.

% complete = 3%
Duration = 167 days
Actual duration = 5.23 days
start = 5/12/05
finish = 12/30/05
status date = 9/17/05

Where can I find information on how summary levels lines are calculated? Or
are they a composite of the tasks beneath?
 
M

Mike Glen

Hi Jweaver ,

Welcome to this Microsoft Project newsgroup :)

Duration of a Summary Task is the working time between the beginning of the
first task to the finish of the last task. If the start date of 12 May is
correct, you need to examine the end date. Try zooming the Gantt chart and
eying down through the tasks to see which one is the last.

FAQs, companion products and other useful Project information can be seen at
this web address: http://project.mvps.org/faqs.htm

Hope this helps - please let us know how you get on :)

Mike Glen
MS Project MVP
 
J

Jweaver

How is "actual duration" calculated at the summary level? Duration appears
to be accurate. It's the actual duration that seems off.
 
M

Mike Glen

Hi,

MVP Steve House once posted:

Sums the Scheduled Durations of the subtasks.
Sums the Actual Durations of the subtasks.
Divides AD/SD to derive an effective % Complete for the group.
Subtracts that from 100 to derive an effective % Remaining for the group.
Multiplies % Remaining * Summary Duration to compute Summary Remaining
Duration
Subtracks SRD from Summary Duration to compute effective Summary Actual
Duration
Adds that to Summary Start date to get effective Completed Through date.


Mike Glen
Project MVP
 
S

Steve House [Project MVP]

The actual duration of a summary task is a weighted average calculation.
First, as noted by another post, the duration of a summary task is the time
between when its earliest starting subtask begins and when its latest
finishing subtask ends. It is not the arithmetic sum of the subtask's
durations except by accident. This is important to remember because the
effective actual duration of the subtask IS based, in part, on the sum of
the subtasks. The calculation is as follows:

1: sum subtasks' durations
2: sum subtasks' actual durations
3: compute subtasks' average % complete by dividing
4: summary % complete = subtask average % complete
5: summary actual duration = summary duration * summary % complete
6: summary remaining duration = summary duration - summary actual duration
7: effective summary completed-through date = summary finish date - summary
remaining duration

Completed through date is calculated by subtracting remaining from finish
date rather than adding actual to start date so that lag times and lead
times in the subtasks are properly accounted for.

HTH
 
J

Jweaver

Thanks, Steve.

Steve House said:
The actual duration of a summary task is a weighted average calculation.
First, as noted by another post, the duration of a summary task is the time
between when its earliest starting subtask begins and when its latest
finishing subtask ends. It is not the arithmetic sum of the subtask's
durations except by accident. This is important to remember because the
effective actual duration of the subtask IS based, in part, on the sum of
the subtasks. The calculation is as follows:

1: sum subtasks' durations
2: sum subtasks' actual durations
3: compute subtasks' average % complete by dividing
4: summary % complete = subtask average % complete
5: summary actual duration = summary duration * summary % complete
6: summary remaining duration = summary duration - summary actual duration
7: effective summary completed-through date = summary finish date - summary
remaining duration

Completed through date is calculated by subtracting remaining from finish
date rather than adding actual to start date so that lag times and lead
times in the subtasks are properly accounted for.

HTH
 

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