Tracking performance over time can be accomplished using either one of two methods which are Run Charts or Control Charts. Both methods use time as the baseline and the performance measure as the measurement that is tracked over time. The major differences in the methods relate to the measures of demarcation on the charts. Run Charts have a center line that represents the mid point of the measurement that is being tracked. Control Charts have a center line that represents the average of the measurement that is being tracked and lines above and below the centerline that are estimates of 3 standard deviations about the average of the measurements.
In both of the charts time is the X axis. The data is plotted in succession over time. The charts can be segmented by specific time periods such as setting the baseline and after improvements have been implemented. You will easily see the before and after results. We can measure the difference between the before average and the after average to calculate the magnitude of the improvement.
Tracking of performance is also a control for maintaining the gains from the improvements. The Run Chart or the Control Chart provides a method to continuously evaluate performance and point out when corrective actions should be taken or when the process should be left alone.
Whenever we contemplate improving a process the baseline for the critical performance metric(s) must be established before any corrective actions are taken. By doing this you will always be able to evaluate the impact of the improvements by measuring from the baseline to the future state of process performance. In the rare case where the corrective action doesn’t work the tracking charts will point that out quickly so an alternative action can be taken. I am sure that you can remember when a great idea just did not work so it is always best to track performance to validate the actual impact of our improvement efforts.