Figure 2

I-chart for waiting time to see a physician. Special-cause variation is identified based on the decision rules: Any single data point outside the 3σ limit; Nine consecutive points fall on the same side of the pre-lean baseline.
I-chart for waiting time to see a physician. Special-cause variation is identified based on the decision rules: Any single data point outside the 3σ limit; Nine consecutive points fall on the same side of the pre-lean baseline.