mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-24 16:42:05 +00:00
73 lines
2.4 KiB
Markdown
73 lines
2.4 KiB
Markdown
---
|
|
slug: /en/sql-reference/aggregate-functions/reference/studentttest
|
|
sidebar_position: 300
|
|
sidebar_label: studentTTest
|
|
---
|
|
|
|
# studentTTest
|
|
|
|
Applies Student's t-test to samples from two populations.
|
|
|
|
**Syntax**
|
|
|
|
``` sql
|
|
studentTTest([confidence_level])(sample_data, sample_index)
|
|
```
|
|
|
|
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.
|
|
The null hypothesis is that means of populations are equal. Normal distribution with equal variances is assumed.
|
|
|
|
**Arguments**
|
|
|
|
- `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).
|
|
- `sample_index` — Sample index. [Integer](../../../sql-reference/data-types/int-uint.md).
|
|
|
|
**Parameters**
|
|
|
|
- `confidence_level` — Confidence level in order to calculate confidence intervals. [Float](../../../sql-reference/data-types/float.md).
|
|
|
|
|
|
**Returned values**
|
|
|
|
[Tuple](../../../sql-reference/data-types/tuple.md) with two or four elements (if the optional `confidence_level` is specified):
|
|
|
|
- calculated t-statistic. [Float64](../../../sql-reference/data-types/float.md).
|
|
- calculated p-value. [Float64](../../../sql-reference/data-types/float.md).
|
|
- [calculated confidence-interval-low.] [Float64](../../../sql-reference/data-types/float.md).
|
|
- [calculated confidence-interval-high.] [Float64](../../../sql-reference/data-types/float.md).
|
|
|
|
|
|
**Example**
|
|
|
|
Input table:
|
|
|
|
``` text
|
|
┌─sample_data─┬─sample_index─┐
|
|
│ 20.3 │ 0 │
|
|
│ 21.1 │ 0 │
|
|
│ 21.9 │ 1 │
|
|
│ 21.7 │ 0 │
|
|
│ 19.9 │ 1 │
|
|
│ 21.8 │ 1 │
|
|
└─────────────┴──────────────┘
|
|
```
|
|
|
|
Query:
|
|
|
|
``` sql
|
|
SELECT studentTTest(sample_data, sample_index) FROM student_ttest;
|
|
```
|
|
|
|
Result:
|
|
|
|
``` text
|
|
┌─studentTTest(sample_data, sample_index)───┐
|
|
│ (-0.21739130434783777,0.8385421208415731) │
|
|
└───────────────────────────────────────────┘
|
|
```
|
|
|
|
**See Also**
|
|
|
|
- [Student's t-test](https://en.wikipedia.org/wiki/Student%27s_t-test)
|
|
- [welchTTest function](welchttest.md#welchttest)
|