**Core Concept:** Measures of dispersion are statistical parameters used to quantify the spread of data points around the central tendency (mean, median, or mode) in a dataset. They provide information on the variability or spread of data.

**Why the Correct Answer is Right:** The correct answer, September 2008, is irrelevant to the context of measures of dispersion as it is a specific date and does not relate to the statistical concepts being tested.

**Why Each Wrong Option is Incorrect:**

A. **Option A:** Standard deviation (SD) is a measure of dispersion that indicates how much the data points deviate from the mean. It is calculated as the square root of the variance (average of squared differences from the mean).

B. **Option B:** Range is a measure of dispersion that represents the difference between the maximum and minimum values in a dataset. It is a simple measure of spread but does not account for the magnitude of deviations.

C. **Option C:** Mean absolute deviation (MAD) is a measure of dispersion that calculates the average of absolute differences between each value and the mean. It is less sensitive to extreme values compared to standard deviation.

D. **Option D:** Coefficient of variation (CV) is a measure of dispersion expressed as a percentage and is calculated as the ratio of standard deviation to mean. It provides a standardized measure of dispersion, allowing comparison across datasets with different units or scales.

**Clinical Pearl:** In clinical practice, understanding measures of dispersion helps interpret the variability of patient data, such as lab results or symptom severity, and allows for comparison and interpretation of data more effectively.

**Correct Answer:** D. Coefficient of variation (CV) is a measure of dispersion expressed as a percentage and is calculated as the ratio of standard deviation to mean. It provides a standardized measure of dispersion, allowing comparison across datasets with different units or scales.