varSamp

Introduced in: v1.1

Calculate the sample variance of a data set.

The sample variance is calculated using the formula:

\frac{\Sigma{(x - \bar{x})^2}}{n-1}

其中:

$x$ 是数据集中的每个数据点
$\bar{x}$ 是数据集的算术平均值
$n$ 是数据集中的数据点数量

该函数假定输入数据集代表从更大总体中抽取的样本。如果您需要计算整个总体的方差(当您拥有完整数据集时),应使用 varPop。

注意

This function uses a numerically unstable algorithm. If you need numerical stability in calculations, use the varSampStable function. It works slower but provides a lower computational error.

Syntax

varSamp(x)

Aliases: VAR_SAMP

Arguments

x — The population for which you want to calculate the sample variance. (U)Int* or Float* or Decimal*

Returned value

Returns the sample variance of the input data set x. Float64

Examples

Computing sample variance

DROP TABLE IF EXISTS test_data;
CREATE TABLE test_data
(
    x Float64
)
ENGINE = Memory;

INSERT INTO test_data VALUES (10.5), (12.3), (9.8), (11.2), (10.7);

SELECT round(varSamp(x),3) AS var_samp FROM test_data;

┌─var_samp─┐
│    0.865 │
└──────────┘

varSamp​

varSamp