The objectives of a quality assurance and control program are to monitor and control analytical measurements to ensure that the limitations of the resulting analytical data are known. Data are continuously monitored by control charts to determine the degree of precision and accuracy. This approach immediately detects outlying data points or other problems in analytical procedures. Assessment on the degree of control of a procedure is then made. When greater confidence is required, the analytical procedure is evaluated in order to make changes to obtain the desired region of statistical control.