In our previous article “What is Earned Schedule” we broke down the basic components of the Earned Schedule calculation and provided an example on how ait can be quickly implemented in a project.

Acumen Fuse provides many metrics to analyse a project schedule, and fortunately Earned Schedule is one of those metrics.

Lets start with a sample schedule in MS Project:

1. MSP Image

Here, the schedule has been baselined and statused to the end of January. We then load it into Acumen Fuse for analysis.

Examining the Earned Schedule Diagnostics tab, we note a Schedule Variance (SV) and Schedule Performance Index (SPI) of -47 and 0.4 respectively.

2. Fuse Diagnostics

From our previous article, we require a baselined and correctly progressed schedule to support the Earned Schedule calculation, using some form of units (hours, cost, quantity) as the basis of Planned Value (PV) and Earned Value (EV).

From this we can calculate Schedule Performance Index and Schedule Variance (SPI(t) and SV(t)).

 

How Does Acumen Fuse Calculate Earned Schedule?

Acumen Fuse doesn’t calculate the Earned Schedule value in its true form, but what it does do is calculate the associated metrics based on activity durations.

By default, Acumen Fuse provides two metrics:

 

Schedule Variance (SV(t)):

SV(t) is noted as the “Calculation of the difference (in days) between the baseline expected progress to date and the actual progress of the activity”.

SUM(

                (

                                IF(ActivityType = "Normal",

                                                IF(ActivityStatus = "Complete",BaselineFinish-ActualFinish,0)

                                                                +

                                                IF(ActivityStatus = "Inprogress",(BaselineFinish - BaselineStart)

                                                                * 

                                                PercentComplete / 100 + BaselineStart - ProjectTimeNow, 0),0

                                                )

                ) * (Start>=_PeriodStart)

)

Note that this calculation is only applied to Tasks and not Milestones. This is quite a complicated formula to potentially implement in a tool such as Microsoft Project however and users may opt for the more standardised evaluation of schedule variance/slippage analysis.

Schedule Performance Index (SPI(t))

SPI(t) in the Acumen Fuse context is the “Ratio showing the performance of the activity relative to the baseline”.

AVERAGE(IF(ActivityStatus = "Complete", (BaselineFinish - BaselineStart) / (ActualFinish - ActualStart), ((BaselineFinish - BaselineStart) - (Finish - ProjectTimeNow)) / (ActualFinish - ActualStart)))

So effectively Acumen Fuse uses days (as its base unit) to determine relative SPI and SV calculations instead of effort, cost or quantity.

 

Can this be applied to MS Project? Well Yes..Sort of!

In our schedule example, we can create a Custom Field in Microsoft Project to calculate the SPI(t) value quite readily.

However it comes with a few caveats.

Lets start by defining a modified version of the SPI(t) formula used by Acumen Fuse:

3. Custom Field

Note here we need to check for tasks that have not started and exclude them along with milestones from the calculation.

For the summary tasks we take the average of it’s child tasks and we are then able to see SPI(t) as a new column:

5. SPI Rollup

Now the issue here is that we should see 0.60 as the SPI(t) for the Design package. Currently it shows 0.45 as it is taking into account the two zero (0) SPI values for other tasks.

To get around this, we could customise a layout that groups the relevant activities as part of the calculation:

6. Alternate Rollup

 

What does this mean?

With some cusomtisation we can start to generate a meaningful SPI value for our schedule without the need to cost load it. Keep in mind it is not the only method of measuring schedule progress and performance. Of course, you could then measure Schedule Variance by examining a simple variance report. 

Alternatively we could define a report in Excel (for example) which accepts Microsoft Project data and runs the calculations for us.

 

Conclusion

If we implement Earned Schedule using the methods described in our previous article (and here) and then compare the SPI and SV outputs to Acumen Fuse outputs, we would no doubt end up with a different answer. Why? The reason is that the method of calculation differs between the two concepts.

On one hand, the standard approach uses units spread over time to arrive at an Earned Schedule value. On the other hand, Acumen expresses the same metrics in terms of days.

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