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65 lines
1.9 KiB
Markdown
65 lines
1.9 KiB
Markdown
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---
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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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对两个总体的样本应用t检验。
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**语法**
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``` sql
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studentTTest(sample_data, sample_index)
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```
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两个样本的值都在 `sample_data` 列中。如果 `sample_index` 等于 0，则该行的值属于第一个总体的样本。 反之属于第二个总体的样本。
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零假设是总体的均值相等。假设为方差相等的正态分布。
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**参数**
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- `sample_data` — 样本数据。[Integer](../../../sql-reference/data-types/int-uint.md), [Float](../../../sql-reference/data-types/float.md) 或 [Decimal](../../../sql-reference/data-types/decimal.md)。
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- `sample_index` — 样本索引。[Integer](../../../sql-reference/data-types/int-uint.md)。
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**返回值**
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[元组](../../../sql-reference/data-types/tuple.md)，有两个元素:
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- 计算出的t统计量。 [Float64](../../../sql-reference/data-types/float.md)。
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- 计算出的p值。[Float64](../../../sql-reference/data-types/float.md)。
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**示例**
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输入表:
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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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查询:
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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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结果:
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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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**参见**
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- [Student's t-test](https://en.wikipedia.org/wiki/Student%27s_t-test)
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- [welchTTest function](../../../sql-reference/aggregate-functions/reference/welchttest.md#welchttest)
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