Figure 2

Clinical record review (CRR) scenarios with adequate power (≥80% ) to detect a 50% (solid line) or 20% (dashed line) reduction in real harm rates (rHR) over a 12-month period. The lines and the zone above and to the right of each line represent CRR scenarios with adequate power. Scenarios vary according to number of practices reviewing records, number of records reviewed per practice and the rHR (indicated by numbers on the lines and measured in incidents/100 patients/year. The median rate ratios (MRR) between patients and between practices were 2 and 1.2 respectively.