A Control Chart is defined as a “chart with control limits in which a statistical measure of a series of samples is plotted in a particular order to guide the process in relation to that measure” (ISO 7870-1:2014), initially developed by Walter Andrew Shewhart (1891–1967), also referred to as Shewhart Control Chart.

Control Charts are applied to monitor any type of process and have been incorporated into laboratory practice, especially after the publication of ISO/IEC 17025 in 1999. Among the requirements of this standard, Assurance of Result Validity establishes that controls must be applied by the laboratory, and the results of these controls must be presented in a way that trends are detected; thus, control charts have always been one of the best options for evaluating such trends.

ConfLab Quality Control Software monitors the analytical process using two types of control charts: “Mean Control Charts” and “Range Control Charts”. These charts automatically perform trend evaluation (which can be defined by the user), with the possibility of working with different action and warning limits (limits calculated from process deviations, limits from uncertainty, maximum limits defined by the user). Thus, this software presents different features such as:

• Process evaluation for limit calculations:
  • Initial outlier evaluation;
  • Systematic error evaluation using the T-test;
  • Determination of calculated limits;
• Definition of chart limits:
  • Determine limits based on uncertainty (which can be imported from the ConfLab Uncertainty software);
  • Determine fixed limits based on user experience, standardized methods, or guidelines;
• Monitoring of result trends:
  • Automatic identification of trends in consecutive values; above the action range; between the action and warning ranges (with number of values defined by the user);
  • Field for recording actions for results outside the established limits;