Statistical Process Control Process control is nothing more or less than monitoring quality as the work is being performed. Perhaps the most widely adopted approach to process control is the use of control charts. Control charts can be developed and used to manage both characteristics (X-bar charts) and attributes ( p-charts). Further, control charts can and should be used throughout the value-added process; that is, in purchasing, production, and logistics operations. Similarly, control charts can be used to improve quality in both manufacturing and service environments. Three types of information must be available to set up a control chart. These are 1) a desired target, 2) a measure of variability around the target, and 3) a managerial assessment of required quality level. The target is generally takes the form of a mean or average; the variability is usually measured via a variance (standard deviation); and the assessment of required quality level is expressed using a z score. It is important to remember that the measure of variability be expressed in terms consistent with the "items" being plotted on the control chart-this usually requires that a standard deviation be transformed into a standard error. When using a control chart, the process operator looks for occurrences when the process is out of control (exceeds control limits) or when "bad" trends emerge. Over time, the causes of these occurrences can be identified and eliminated such that the process is improved continually. Finally, remember that the process must be in control when the control chart is set up (otherwise GIGO!). F Twenty samples of four items each were taken to set up the control chart. The design target =2.80cm. Problem: Set up a control chart. After the control chart was established, daily sampling began as follows: Do you see any trends? Is the operation in control