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638 – New Approaches to Disclosure-Safe Dissemination of Medicare Claims Data
A Note on the Design and Implementation of a Phase II Distribution-free CUSUM Exceedance Control Chart for Monitoring Unknown Location
Marien Graham
University of Pretoria
Subha Chakraborti
The University of Alabama
Amitava Mukherjee
Indian Institute of Management
We examine several aspects related to the efficient design and implementation of a class of Phase II nonparametric cumulative sum (CUSUM) charts based on the exceedance statistic. First, we investigate which order statistic (percentile), from the reference (Phase I) sample, should be used to obtain the best performance. It is observed that other choices than the median, such as the third quartile, can play an important role in improving the performance of the chart. Next, we study different choices of the CUSUM design parameter, k, called the reference value. Moreover, although the most widely used chart performance metric is the average run-length (ARL), certain shortcomings have been observed and instead we use more representative measures for the assessment of chart performance. These include other percentiles of the run-length, more specifically, the median run-length (MRL), which provides additional and more meaningful information about the in-control and out-of-control performances of control charts, not given by the ARL. The procedures are illustrated with some data. A summary and some concluding remarks are given.