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68 lines
1.4 KiB
Markdown
68 lines
1.4 KiB
Markdown
---
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title: "varSamp"
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slug: /en/sql-reference/aggregate-functions/reference/varSamp
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sidebar_position: 212
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---
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## varSamp
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Calculate the sample variance of a data set.
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**Syntax**
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```sql
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varSamp(x)
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```
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Alias: `VAR_SAMP`.
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**Parameters**
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- `x`: The population for which you want to calculate the sample variance. [(U)Int*](../../data-types/int-uint.md), [Float*](../../data-types/float.md), [Decimal*](../../data-types/decimal.md).
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**Returned value**
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- Returns the sample variance of the input data set `x`. [Float64](../../data-types/float.md).
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**Implementation details**
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The `varSamp` function calculates the sample variance using the following formula:
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$$
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\sum\frac{(x - \text{mean}(x))^2}{(n - 1)}
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$$
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Where:
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- `x` is each individual data point in the data set.
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- `mean(x)` is the arithmetic mean of the data set.
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- `n` is the number of data points in the data set.
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The function assumes that the input data set represents a sample from a larger population. If you want to calculate the variance of the entire population (when you have the complete data set), you should use [`varPop`](../reference/varpop.md) instead.
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**Example**
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Query:
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```sql
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DROP TABLE IF EXISTS test_data;
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CREATE TABLE test_data
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(
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x Float64
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)
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ENGINE = Memory;
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INSERT INTO test_data VALUES (10.5), (12.3), (9.8), (11.2), (10.7);
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SELECT round(varSamp(x),3) AS var_samp FROM test_data;
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```
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Response:
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```response
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┌─var_samp─┐
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│ 0.865 │
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└──────────┘
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```
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