When using MS Project Desktop Pro, Math calculation is wrong

Question

See above Screen shot- This calculation is incorrect and the support team reports the following:

We were able to find the below mentioned observations:

1. Scheduling practice is not properly followed.
2. The way we want to design our tasks, Manual Scheduling should be followed.
3. Start date of "Task 44" is scheduled to start before the project start date.
4. Duration will not calculate these tasks the way we want because of Auto Scheduling.
5. We need to add "Work" column then only you will the expected results.

My manager is a tenured MS project user and said this is a bogus response, the math is simply wrong,

Has anyone else had this issue? We have noticed it in several Projects,

Thank you, Anne

Answer 1

Anne Shields,

1. What scheduling practice is not being followed? There are several things I see which are not good practice, such as manually scheduled tasks, blank predecessors, predecessors on summaries.
2. Manual scheduling is a waste of time, except as John says for early roughing out.
3. Can't see 44, but so what?
4. Auto scheduling calculates the duration. It's arithmetic. Don't know what you want, but arithmetic trumps opinion.
5. Go ahead and display the work column/field. You will see the work. Apart from that, what is expected?

the calculation is definitely correct. Look at the bars on the chart. This is how it looks when the standard calendar is the project/task calendar, and with the time displayed as well as the date. With 16 hours duration it is not exactly like yours, 17 hours, so I suspect that you may have a different calendar or the perhaps earliest task starting at 07:00.

Answer 2

Anne --

No, I doubt that the calculation is wrong. And I suspect your manager is wrong as well.

There is something you are not seeing in the project that you actually do need to see, which is the date AND time of each task's Start date and Finish date. Click File > Options. On the General page of the Project Options dialog, click the Date Format pick list and select the 1/28/09 12:33 PM item at the top of the pick list. Click the OK button to apply this setting to your copy of Microsoft Project.

Widen the Start and Finish columns so that you can see the full date and time information for each task. When you examine this information for the P1 Testing summary task, I believe you will see that the task spans 17 hours from the Start date and time of the earliest staring milestone subtask to the Finish date and time of the latest finishing milestone subtask.

Microsoft Project always calculates the Duration of a summary task from the start of its earliest starting subtask to the finish of its latest finishing subtask. It DOES NOT calculate the Duration of a summary task by summing the Duration values for its subtasks.

Does this explain your situation? Please let us know and we will try to help you.

Answer 3

Anne Shields,

My response to the "observations"

1. What scheduling practice exactly is not being followed?
2. The task mode (auto/manual) you select is up to the user but manual scheduling should only be used for initial development of a plan (i.e. rough draft) and not be used once a plan is ready for execution. Otherwise, you might as well use Excel for scheduling.
3. Again, whether some tasks are set to start before the project start date is determined by how the user sets up the plan. If your options are set to show scheduling alerts Project will notify you of "early" start tasks.
4. How exactly do you want duration to be calculated?
5. So what are the "expected" results?

It's impossible to determine is the 17h duration of summary line 12 is correct or not. What is your definition of a day? How many work hours per day in your project calendar? What is the start TIME and finish TIME for that summary line? For example, given a normal Standard calendar with a default 8 hour work day, if summary line 12 starts at 4:00 PM on 7/1/22 and finishes at 5:00 PM on 7/1/22, then the summary line duration is indeed 17 hours.

John