1.1 This practice provides guidance for the use of control charts in statistical process control programs, which improve process quality through reducing variation and controlling the process to a particular target level or historical average.
1.2 Control charts are used to monitor product or process characteristics to determine whether or not a process is in a state of statistical control. When this state is attained, the true mean and the true standard deviation of that characteristic are constant.
1.3 This practice applies to variables data (characteristics measured on a continuous numerical scale) and to attributes data (characteristics measured as percentages, fractions, or counts of occurrences in a defined interval of time or space).
1.4 The system of units for this practice is not specified. Dimensional quantities in the practice are presented only as illustrations of calculation methods. The examples are not binding on products or test methods treated.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.