Laboratory Quality Control Practice Test

The coefficient of variation expresses variability as a percentage by normalizing the spread of the data (standard deviation) to the average value (mean). It’s calculated as CV = (SD / mean) × 100%. Because it’s expressed relative to the mean, it lets you compare precision across datasets or methods that have different units or scales. A smaller CV means the data are tightly clustered around the mean, indicating more consistent results; a larger CV indicates greater relative variability. Standard deviation measures dispersion in the same units as the data, not as a percentage. Range shows the absolute spread between the smallest and largest values, also not a percentage. Mean describes central tendency, not variability. Note that CV can become unstable when the mean is near zero, since dividing by a small number inflates the result.