Last month,’ we described Continuous Quality Improvement (CQI), a general model for quality in any organized activity. CQI grew out of the concepts of Statistical Process Control developed in the 1930s by statistician Walter Shewhart. Shewhart believed that by measuring the outputs of any process, one could differentiate between variation from random fluctuations and variation that represented a loss of control over the process. Processes whose outputs remained within their control limits were considered to be under control. Processes that transgressed their control limits were out of statistical control, and adjustments were needed to return the process to control. The workers responsible for the processes could make the needed measurements and maintain the control charts themselves, allowing rapid detection and correction of unacceptable variation and enhancing the workers' sense of responsibility for the quality of the product.
A number of theoreticians, particularly W. Edwards Deming, Joseph M. Juran, and Philip B. Crosby, built on these concepts to develop CQI (also known as total quality management, total quality control, or industrial quality control). In CQI, quality is achieved through “a continuous effort by all members of the organization to meet the needs and expectations of the customer.” The term “customer” includes every person or group, within or outside the organization, who depends on the efforts or outputs of workers within the organization.