QC tests are plotted using which symbol?

The correct answer is the symbol X. In quality control and testing scenarios, the X symbol is commonly used to denote a specific value or test result in various graphical representations and control charts. It serves as a clear and recognizable marker that indicates a data point related to Quality Control (QC) tests.

Using the X symbol helps to distinguish QC results from other types of data that may also be plotted, such as measurements or averages. This distinction enables easier analysis and interpretation of quality data over time, as patterns or trends can be quickly identified.

Other symbols, while potentially used in different contexts, do not carry the same standardized meaning in relation to QC testing. For example, the O symbol may represent a different data point or status in other applications, while the √ symbol often indicates correctness or validation rather than being used for plotting test results. Similarly, the Δ symbol generally signifies change or difference, which is not fitting for directly representing QC test data. Understanding these symbolic conventions is essential for clear communication in the field of quality control.