In a Levey-Jennings plot, which statement is true about axes?

In a Levey-Jennings plot, which statement is true about axes?

• A. X-axis represents time
• B. Y-axis represents time
• C. Both axes represent time
• D. On the plot, time is represented on the X-axis

Answer: (D)

In a Levey-Jennings plot, you’re tracking a single measurement over time or across sequential runs, so the horizontal axis represents the progression of testing (time or run order) and the vertical axis shows the actual result value. This layout lets you see how the measured value behaves as tests are done over days or across batches, making it easier to spot trends, drifts, or out-of-control points relative to the mean and the control limits. The reason this arrangement is the best is that the whole purpose is to monitor stability of a result over time. If time were plotted on the vertical axis, you wouldn’t be able to readily assess how the value changes from one run to the next, and plotting time on both axes would remove the meaningful differentiation between sequence and magnitude. The vertical axis must represent the measurement itself, while the horizontal axis provides the time or run sequence context.

In a Levey-Jennings plot, you’re tracking a single measurement over time or across sequential runs, so the horizontal axis represents the progression of testing (time or run order) and the vertical axis shows the actual result value. This layout lets you see how the measured value behaves as tests are done over days or across batches, making it easier to spot trends, drifts, or out-of-control points relative to the mean and the control limits.

The reason this arrangement is the best is that the whole purpose is to monitor stability of a result over time. If time were plotted on the vertical axis, you wouldn’t be able to readily assess how the value changes from one run to the next, and plotting time on both axes would remove the meaningful differentiation between sequence and magnitude. The vertical axis must represent the measurement itself, while the horizontal axis provides the time or run sequence context.