Figure 2.

CUSUM Analysis for device success. Incremental line represents unadjusted cumulative sum of failures. Lower and upper limits are calculated upon acceptable and unacceptable failure rates of 5% and 10%, respectively. Observations above the upper limit indicate out of control procedure, while observation below the lower limit suggest better-than-expected results (proficiency). CUSUM analyses are provided for the overall population (A), low-intermediate risk (B), and high-risk subgroups (C).