On a QC chart, which option describes the measurement displayed on the plot?

• A. It displays the time
• B. It displays the test count
• C. It displays the measured control value
• D. It displays calibration values

Answer: (C)

The key idea is that a QC chart shows the actual numeric result obtained from the control sample in each run. Each plotted point represents the measured control value, so you can see how the instrument and process are performing over time and whether those measurements stay within predefined control limits. Time or run order usually appears on the horizontal axis, not as the measurement itself. Calibration values are used for adjusting or validating the instrument, not the data point being tracked on the QC chart. So the measurement displayed is the measured control value.