Mean, median, mode, variance, and other descriptive statistics measures and how each is calculated. Front: the term or formula. Back: definition or formula with a brief usage note.
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- Mean
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Sum of all values divided by the number of values; the arithmetic average.- Median
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The middle value when data is ordered; the 50th percentile.- Mode
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The most frequently occurring value in a dataset.- Weighted mean
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Sum of each value multiplied by its weight, divided by the sum of weights; used when values have different importance.- Geometric mean
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The nth root of the product of n values; useful for growth rates and investment returns.- Range
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The difference between the largest and smallest values.- Population variance
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The average of squared deviations from the population mean, denoted by sigma squared.- Sample variance
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The sum of squared deviations from the sample mean divided by n-1; provides an unbiased estimate of population variance.- Population standard deviation
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The square root of population variance; measures spread in the same units as the data.- Sample standard deviation
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The square root of sample variance; estimates the population standard deviation with minimal bias.- Coefficient of variation
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Standard deviation divided by the mean, often expressed as a percentage; allows comparison of spread across different scales.- Interquartile range (IQR)
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The difference between the third quartile (Q3) and first quartile (Q1); contains the middle 50% of data.- Mean absolute deviation
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The average of the absolute values of deviations from the mean; another measure of spread.- Percentile
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A value below which a given percentage of observations fall; ranges from 0 to 100.- Quartile
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Values that divide ordered data into four equal parts: Q1 (25th), Q2 (50th), Q3 (75th), Q4 (100th).
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