Using Task Duration as a Quantity
Extreme caution should be exercised when using Task Duration as a quantity to generate S‑curves.
Consider the following Production Schedule.
MH per Day
Task No. 1
Task No. 2
Task No. 3
Task No. 4
Table 12: Production Schedule
The % Complete values represent the Task's physical percentage completion, as inspected on 4th February 2016 (The Cut Off Date).
Task Duration S-curves
The S-curves generated using Task Duration as the Quantity are shown in Figure 20.
Figure 20: Percentage Task Duration S-curves (Target = 100%)
Analysis of the above S-curves reveals the Project as of the 4th of February 2016:
- Is 27.86% Complete (Actual)
- Should be 42.86% Complete (Target)
- Is 15.00% behind target (42.86 - 27.86)
Task Man Hour S-curves
The S-curves generated using Task Man Hours as the Quantity are shown in Figure 21.
Figure 21: Percentage Task Man Hours S-curves (Target = 100%)
Analysis of the above S-curves reveals the Project as of the 4th of February 2016 is:
- 7.95% Complete (Actual)
- Should be 13.00% Complete (Target)
- 5.05% behind target (13.00 - 7.95)
A comparison of the above figures reveal using Task Duration as a quantity paints a very different picture of the Project's progress as compared to using Task Man Hours as a quantity.
The reason for the variance in the Project's progress is that by using Task Duration as a quantity, the assumption is all Tasks require exactly the same amount of Man Hours per Day. This is often not the case in real life.
In Part 4 I will justify why S-curves are so important as a reporting tool