what is sd

The full English name of

sd is "Standard Deviation", which is the standard deviation. In the Chinese environment, it is often called the mean square error, but unlike the mean square error, the standard deviation is the square root of the sum of the squares of the mean deviations. , represented by the "σ" symbol.

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Standard Deviation (Standard Deviation), in the Chinese environment It is often called the mean squared error, but it is different from the mean squared error. The mean squared error is the average of the squared distances of each data from the true value, that is, the average of the sum of squared errors. The calculation formula is close to the variance in form, and its The square root is called the root mean square error, and the root mean square error is formally close to the standard deviation). The standard deviation is the square root of the average sum of the squares of the mean deviation, represented by σ.

The standard deviation is the arithmetic square root of the variance. Standard deviation reflects the dispersion of a data set. If the means are the same, the standard deviations may not be the same.

Standard Deviation is most commonly used in probability statistics as a measure of statistical distribution. The standard deviation is defined as the square root of the arithmetic mean of the squared deviations of the standard values ​​of each unit in the population from its mean. It reflects the degree of dispersion among individuals within a group. The result of measuring the degree of distribution has two properties in principle:

is a non-negative value and has the same unit as the measurement data. There is a difference between the standard deviation of a total quantity or a random variable and the standard deviation of a subset of samples. Standard calculation formula:

Suppose there is a set of values ​​​​X₁,

Standard deviation is also called standard deviation, or experimental standard deviation. The formula is

Simply put, standard deviation is the dispersion of the average value of a set of data A measure of degree. A larger standard deviation means that most values ​​are significantly different from the mean; a smaller standard deviation means that most values ​​are closer to the mean.

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