8-5. Critical ratio

In addition to variance analysis and earned value analysis, another tool for project control is the Critical Ratio analysis. The critical ratio CR= CPIxSPI.

The ideal CR will be 1.0  Ratios greater than 1.0 imply project doing well on both cost and schedule while ratios below 1.0 imply poor performance.

A useful guide might be the use of a chart to show the CR over time and when intervention (control) might be needed.  An example is attached critical-ratio-graph

The graph shows in one example when ratios above and below 1.0 might be ignored and when project management action is needed.