Which of the following is MOST important to ensure confidence in analytical testing results?

• A. Repeatability
• B. Means of reporting
• C. Clean bottles
• D. Quality control results

Answer: (D)

Confidence in analytical testing results comes from evidence that the measurement system is performing correctly. Quality control results provide that evidence by showing how well the method is working through controls like blanks, calibration checks, duplicate samples, and spike recoveries. When QC results stay within established criteria, you can trust the reported values because they demonstrate accuracy, precision, and lack of bias across runs and conditions. If QC results fail, it signals potential problems in the method or instrument, prompting investigation or reanalysis. While repeatability speaks to precision in a single run and clean bottles reduce contamination risk, neither alone proves that the overall method is reliable. How results are reported matters for communication, but not for confirming their validity. Therefore, quality control results are the most important factor for confidence in analytical results.