We often analyze data, looking first to address variances among the people engaged in the work. What if the practice itself is faulty? W. Edwards Deming, as a principle of his work on quality and continuous improvement would focus primarily on the practice. “I am not reporting things about people. I am reporting things about practices.”
If you have variance amongst the people performing the work, you still have no assurance that the currently designated practice is the ideal one. Higher level performers may simply be performing an illogical practice exceedingly well, with no guarantee of the desired result. Current lower level performers could actually be closer to performing an ideal practice with their efforts, but the wrong practice and the wrong measures may still prevail.
Also worth examining, are the lines of accountability for the practices you have in place. In some cases, the responsibilities assigned are well beyond the control of an individual performer. Another clarifying Deming principle denotes: “Divide responsibility and nobody is responsible.”
In your pursuit of excellence, look first (and throughout) at your defined practices and not just the people engaging in the work. The “playbook” for the practices to be performed with excellence is the responsibility of leadership with their teams. Setting the stage for excellence involves the precise alignment of the ideal practices, clarified expectations with each individual and the precise utilization of measures or reports to continuously improve.