Schedule Compression Index (SCI) is a CPM industry standard metrics designed to quantify the value of “schedule compression” that has occurred between either 2 schedule updates or 1 update and the baseline schedule. Deriving the Schedule Compression Index for any Project works best when there are minimal activity count changes between the 2 selected updates.
For example, if the selected Modified Project has the same number of activities as the selected Control Project, then the SCI will yield a more accurate result. Whereas, if the number of activities between the 2 Project updates are significantly different, the SCI value will be less accurate.
In the figure above, the Control Project’s update shows Activity A in progress with successors Activities B, C and D. In the Modified Project’s update, Activity A is complete, however later than compared to is Control Early Finish date. The Modified’s Project Update overall completion is maintained by reducing the remaining duration in Activities B, C and D. Therefore, by observation, the Modified Update reflects a level of schedule compression to maintain the Project Finish date.
In the figure above, the equation to calculate the SCI is shown. Note that the Remaining Early Start Date (RES) is calculated by subtracting the Remaining Calendar Duration from the Control Early Finish date. Since Activity B is “in progress” in the Modified update, the RES is later than Activity B’s Early Start. This allows for taking account for partial progress achieved in the Modified Project’s update.
Ƶümmer’s Schedule Compression Index Report, shown above, displays each task that is not complete in the Modified Project’s update, then shows the Remaining Calendar Duration, Control Remaining Early Start (RES) date, “Control Early Finish” (CEF) date, Modified Early Start (MES) date and Modified Early Finish (REF) date. At the completion of the listing, the Minimum RES, Maximum CEF, Minimum MES and Maximum MEF dates are calculated. Below that, the overall durations for the SCI calculation are shown. In the example below the Schedule Compression Index is shown as 41.61%. Finally, the RES and SCI equations are shown at the bottom of the report.
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