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Coefficient of Variation

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Coefficient of Variation (CV)

Definition

The Coefficient of Variation (CV) is a standardized measure of dispersion that expresses variability relative to the mean. It's particularly useful when comparing datasets with different units or widely different means.

Formula

Sample Coefficient of Variation:

CV=sxˉ×100%CV = \frac{s}{\bar{x}} \times 100\%

Population Coefficient of Variation:

CV=σμ×100%CV = \frac{\sigma}{\mu} \times 100\%

Where:

  • ss = sample standard deviation
  • xˉ\bar{x} = sample mean
  • σ\sigma = population standard deviation
  • μ\mu = population mean

Example

Consider two datasets:

Dataset A (temperatures in °C): 20,22,21,23,1920, 22, 21, 23, 19

Dataset B (heights in cm): 160,165,162,168,155160, 165, 162, 168, 155

Dataset A:

Mean=21 °CStandard Deviation=1.58 °CCV=1.5821×100%=7.52%\begin{align*} \text{Mean} &= 21\text{ °C} \\ \text{Standard Deviation} &= 1.58\text{ °C} \\ CV &= \frac{1.58}{21} \times 100\% = 7.52\% \end{align*}

Dataset B:

Mean=162 cmStandard Deviation=4.85 cmCV=4.85162×100%=2.99%\begin{align*} \text{Mean} &= 162\text{ cm} \\ \text{Standard Deviation} &= 4.85\text{ cm} \\ CV &= \frac{4.85}{162} \times 100\% = 2.99\% \end{align*}

Although Dataset B has a larger standard deviation, its CV is smaller, indicating less relative variability.

Key Points

  • Only applicable to ratio scale data with positive values and non-zero mean
  • Useful for comparing variability between datasets with different units or means
  • Generally expressed as a percentage

Common Interpretations

CV < 10%: Very low variability relative to the mean
10% ≤ CV < 20%: Low variability relative to the mean
20% ≤ CV < 30%: Moderate variability relative to the mean
CV ≥ 30%: High variability relative to the mean

Limitations

  • Not meaningful for interval or ordinal scale data
  • Cannot be calculated for data with zero mean or negative values
  • Sensitive to outliers, like other measures based on mean and standard deviation

Related Links

Mean, Median, Mode Calculator

Range, Variance, Standard Deviation Calculator

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