Discussion

How is BCWP calculated

January 24, 2013 - 02:26 am
3 comment(s)

How is BCWP, ACWP, BCWS calculated?

In ProjectLibre 1.5.3 on Ubuntu , I do the following:

1. Create task of 1 week
2. Assign it to a ressource with a salary of 10 euros per hour
3. Cost ends being 400
4. Save baseline in the default baseline
5. BCWS = 80 euros
6. Change % achevé (I belive this would be % done) to 10%
7. BCWP = 40 euros, ACWP = 40 euros
8. Change % done to 30%
9. BCWS = BCWP = ACWP = 80 euros

I would have expected
BCWS = 400 (same as cost)
BCWP = 120
ACWP = 120

Is this a known issue or is something in earned value theory escaping me?

3 Comments

January 24, 2013 - 02:46 am

 

  Scheduling a 2 day task ending before the current date with a cost of 160$ does make the BCWS = cost, as I would expect. 

 So BCWS depends on the current date.  Makes sense.

Now I'm going to check if the figures have the values I expect if I finish them ahead of time.

January 24, 2013 - 03:06 am

So here's another oddity.

If I have a task that is performed ahead of time, the SPI is will 1.

The reason is that BCWP can't go over BCWS.

1. Create a new project with a start date a month earlier than current date

2. Create a task that starts before current date and ends after current date with the duration of 5 days

3. Assign it to a ressouce with a standard rate of 10 units per hour.

4. Costs should be 400

5. Save baseline

6. BCWS ends up being between 0 and 400

7. Set % done to 10%.

8. Observe SPI as you increment % done.  SPI will start below 1 and gradually reach 1 where it will stop incrementing.

9. I would expect once it reaches 100% that the SPI would be above 1.

Known issue?  What am I missing?

January 24, 2013 - 11:34 am

Found in openproj_core/src/com/projity/pm/assignment/Assignment.java

1490 //[(Actual % of completion / Expected % of completion) of an activity for a given period] * Actual cost of activity
1491 public double bcwp(long start, long end) {

I would have expected

BCWP = %done * BAC.

Moreover, I wouldn't have expected the actual cost to be a variable in how BCWP is calculated. Wikipedia states:

"Suppose that by the end of January 5, the work is actually only 30% complete. In this case,

the BCWP would be $1000 (budgeted cost) times 30% (the actual completion percentage), or $300."

Indeed, budgeted cost, not actual cost, are taken into account.

http://en.wikipedia.org/wiki/Budgeted_cost_of_work_performed

What am I missing?