standard deviation

American  

noun

Statistics.

1. a measure of dispersion in a frequency distribution, equal to the square root of the mean of the squares of the deviations from the arithmetic mean of the distribution.

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standard deviation British  

noun

1. statistics a measure of dispersion obtained by extracting the square root of the mean of the squared deviations of the observed values from their mean in a frequency distribution

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standard deviation Scientific  

/ stăn′dərd /

1. A statistic used as a measure of the dispersion or variation in a distribution, equal to the square root of the arithmetic mean of the squares of the deviations from the arithmetic mean.

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standard deviation Cultural  

1. In statistics, a measure of how much the data in a certain collection are scattered around the mean. A low standard deviation means that the data are tightly clustered; a high standard deviation means that they are widely scattered.

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Discover More

About sixty-eight percent of the data are within one standard deviation of the mean.

Etymology

Origin of standard deviation

First recorded in 1920–25

Compare meaning

How does standard-deviation compare to similar and commonly confused words? Explore the most common comparisons:

• standard deviation vs. standard error

Example Sentences

See Examples For:

standard deviation

The intervention raised math achievement by 0.184 standard deviation a year in elementary school and 0.146 in secondary school.

From The Wall Street Journal ● Jul. 24, 2026

Economists estimate each standard deviation of achievement is worth $110,000 to $230,000 in lifetime earnings, so $10 billion buys roughly three years of that gain for two million children, about a $200 billion increase.

From The Wall Street Journal ● Jul. 24, 2026

Our visual impression is confirmed by the data: The standard deviation of the HSNSI’s daily values since the beginning of 2025 has been 31% higher than the prior 25 years’ average.

From MarketWatch ● Jul. 7, 2026

Their final result brought theoretical predictions and experimental measurements into agreement within less than half a standard deviation.

From Science Daily ● May 19, 2026

No other breed falls outside the standard deviation.

From "The Miscalculations of Lightning Girl" by Stacy McAnulty