On a Levey-Jennings Chart, what is the typical acceptable range for control values?

On a Levey-Jennings Chart, what is the typical acceptable range for control values?

• A. Mean ± 2SD
• B. Mean ± 1SD
• C. Mean ± 3SD
• D. Mean ± 4SD

Answer: (A)

On a Levey-Jennings chart, control results are plotted with a central line for the mean and bands at fixed multiples of the standard deviation. The typical acceptable range is the mean plus and minus two standard deviations. This mirrors the normal distribution idea that about 95% of normal results should fall within two SD of the mean, giving a practical balance between catching real issues and not overreacting to normal variation. If a control value lands outside this band, it prompts investigation into potential shifts or errors. Using only one SD would flag too many results as out of control, while using three SD would be too permissive and may miss problems.

On a Levey-Jennings chart, control results are plotted with a central line for the mean and bands at fixed multiples of the standard deviation. The typical acceptable range is the mean plus and minus two standard deviations. This mirrors the normal distribution idea that about 95% of normal results should fall within two SD of the mean, giving a practical balance between catching real issues and not overreacting to normal variation. If a control value lands outside this band, it prompts investigation into potential shifts or errors. Using only one SD would flag too many results as out of control, while using three SD would be too permissive and may miss problems.