standard deviation


General Science

  • noun a measure of the amount by which a set of values differs from the arithmetic mean



  • A statistic, used as a measure of dispersion in a distribution, that is equal to the square root of the arithmetic average of the squares of the deviations from the mean.


  • noun the measure of how much a variable changes from its mean


  • A statistical measure of the dispersion or spread around the mean, for a given set, series, or population. It is equal to the square root of the variance. If a data set has as a bell-shaped distribution, for instance, 68.3% of the data will fall on either side of one standard deviation, 95.5% within two standard deviation, 99.7% within three, and so on. Its abbreviation is SD. Its symbol is σ.

Health Economics

  • (written as Standard Deviation)
    The standard deviation (SD) is measure of the dispersion of a set of numbers around the mean value of a variable. It is the square root of the variance. A large value of SD implies a large dispersion about the mean and vice versa.

Information & Library Science

  • noun a statistical term to show how far things are different from the normal