Some Problems with Individual Control Charts, as Taught and as Practiced

Joyce Nilsson Orsini, Ph.D


After having been buried for some fifty years, individual control charts have surfaced again and are gaining in popularity, much to the embarrassment of the statistical community. Individuals charts are not control charts. This presentation will clarify the differences between the two types of charts and explain the dangers of substituting one for the other. A number of companies have been misled when using individuals charts to analyze process control. Examples will be provided from industry, service and government. One example will show how an organization lost $4 million due to its belief that an individuals chart was actually a control chart.