Measures of Spread

Statistics · Axiom Academy

Understanding how data varies around the center Consider two classes with the same average test score of 75. In Class A, all students scored between 70-80. In Class B, scores ranged from 40-100. The mean alone doesn't reveal this crucial difference in variability. 2. Range and Interquartile Range (IQR) The range is the simplest measure: maximum minus minimum. However, it's sensitive to outliers. The IQR (Q3 - Q1) measures the spread of the middle 50% of data, making it more robust. 3. Variance: Measuring Deviations Variance measures the average squared distance of each data point from the mean. We square the deviations to avoid negative values canceling out positive ones, and to give more weight to extreme values. 4. Standard Deviation: Spread in Original Units Standard deviation is the square root of variance. This brings our measure back to the original units of the data, making it more interpretable. It represents a "typical" distance from the mean.

This is the written version of the interactive lesson above. See the full Statistics course.