On a Levey-Jennings plot, dispersion refers to what pattern?

• A. Increased frequency of both high and low numbers
• B. Increased high values only
• C. Increased low values only
• D. Stable values

Answer: (A)

Dispersion is about how spread out the QC results are around the mean on a Levey-Jennings plot. When dispersion increases, the points scatter more widely and appear on both sides of the mean, not just above or below it. This means greater random variation (a larger standard deviation) and more values away from the target. If you saw results clustering toward high values only, that would indicate a bias upward; toward low values only would be a bias downward; tightly clustered points mean stable measurements. So the pattern associated with dispersion is more high and more low values occurring, i.e., increased spread on both sides of the mean.