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67 lines
2.1 KiB
Markdown
67 lines
2.1 KiB
Markdown
---
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toc_priority: 300
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toc_title: studentTTest
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---
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# studentTTest {#studentttest}
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Applies Student's t-test to samples from two populations.
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**Syntax**
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``` sql
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studentTTest(sample_data, sample_index)
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```
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Values of both samples are in the `sample_data` column. If `sample_index` equals to 0 then the value in that row belongs to the sample from the first population. Otherwise it belongs to the sample from the second population.
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The null hypothesis is that means of populations are equal. Normal distribution with equal variances is assumed.
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**Arguments**
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- `sample_data` — Sample data. [Integer](../../../sql-reference/data-types/int-uint.md), [Float](../../../sql-reference/data-types/float.md) or [Decimal](../../../sql-reference/data-types/decimal.md).
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- `sample_index` — Sample index. [Integer](../../../sql-reference/data-types/int-uint.md).
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**Returned values**
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[Tuple](../../../sql-reference/data-types/tuple.md) with two elements:
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- calculated t-statistic. [Float64](../../../sql-reference/data-types/float.md).
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- calculated p-value. [Float64](../../../sql-reference/data-types/float.md).
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**Example**
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Input table:
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``` text
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┌─sample_data─┬─sample_index─┐
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│ 20.3 │ 0 │
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│ 21.1 │ 0 │
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│ 21.9 │ 1 │
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│ 21.7 │ 0 │
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│ 19.9 │ 1 │
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│ 21.8 │ 1 │
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└─────────────┴──────────────┘
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```
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Query:
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``` sql
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SELECT studentTTest(sample_data, sample_index) FROM student_ttest;
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```
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Result:
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``` text
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┌─studentTTest(sample_data, sample_index)───┐
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│ (-0.21739130434783777,0.8385421208415731) │
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└───────────────────────────────────────────┘
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```
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**See Also**
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- [Student's t-test](https://en.wikipedia.org/wiki/Student%27s_t-test)
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- [welchTTest function](welchttest.md#welchttest)
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[Original article](https://clickhouse.tech/docs/en/sql-reference/aggregate-functions/reference/studentttest/) <!--hide-->
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