MySQL STDDEV_SAMP() function

STDDEV_SAMP() function

MySQL STDDEV_SAMP() function returns the sample standard deviation of an expression ( the square root of VAR_SAMP()). Statistically, sample standard deviation quantifies the amount of variation or dispersion in a dataset for which you have a sample of the whole population.

It returns NULL if no matching rows are found.

This function is useful in -

  • It's used when you have a sample of data and want to estimate the variability in the entire population.
  • Data Analysis: The primary purpose of the STDDEV_SAMP() function is to accurately calculate the sample standard deviation.
  • When comparing different samples or groups, STDDEV_SAMP() is used to assess the significance of differences between the groups.
  • Sample standard deviation is used to calculate confidence intervals for population parameters based on sample data.
  • STDDEV_SAMP() is used to explore the variation and distribution of data in sample datasets, helping in initial data analysis.
  • Sample standard deviation is used in hypothesis testing to test the validity of assumptions and draw conclusions about population characteristics.



Where expr is an expression.

MySQL Version: 8.0

Example: MySQL STDDEV_SAMP() function

The following statement returns the sample standard deviation of 'total_cost' from purchase table.

Sample table: purchase


FROM purchase;


mysql> SELECT STDDEV_SAMP(total_cost)
    -> FROM purchase;
| STDDEV_SAMP(total_cost) |
|              345.494814 | 
1 row in set (0.00 sec)

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