To evaluate and approve reportable results, checks should be performed on sampling, sample handling and storage, methodology, calibration, and quality control. If any problems arise through doubtful data, initiation of corrective actions and providing the final approved results is the responsibility of the analyst, the laboratory supervisor, and the QC department. No data should be released until statistically supported limits are reported for them. Data should be technically sound and defensible before they can be reported. The first requirement for reporting is that all pertinent documentation is available and referenced so that it can be found at any time it might be needed. Calibration in chemical measurements refers to the process by which the response of a measurement system is related to the different concentrations of the analyte of interest. Analytical data for each parameter, produced by the analyst, are checked by QC acceptance criteria, validated, corrected if necessary, and then converted to a reportable value.