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73 lines
2.5 KiB
Markdown
73 lines
2.5 KiB
Markdown
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---
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toc_priority: 310
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toc_title: mannWhitneyUTest
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---
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# mannWhitneyUTest {#mannwhitneyutest}
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对两个总体的样本应用 Mann-Whitney 秩检验。
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**语法**
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``` sql
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mannWhitneyUTest[(alternative[, continuity_correction])](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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零假设是两个总体随机相等。也可以检验单边假设。该检验不假设数据具有正态分布。
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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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**参数**
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- `alternative` — 供选假设。(可选，默认值是: `'two-sided'` 。) [String](../../../sql-reference/data-types/string.md)。
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- `'two-sided'`;
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- `'greater'`;
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- `'less'`。
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- `continuity_correction` — 如果不为0，那么将对p值进行正态近似的连续性修正。(可选，默认：1。) [UInt64](../../../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U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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│ 10 │ 0 │
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│ 11 │ 0 │
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│ 12 │ 0 │
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│ 1 │ 1 │
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│ 2 │ 1 │
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│ 3 │ 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 mannWhitneyUTest('greater')(sample_data, sample_index) FROM mww_ttest;
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```
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结果:
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``` text
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┌─mannWhitneyUTest('greater')(sample_data, sample_index)─┐
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│ (9,0.04042779918503192) │
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└────────────────────────────────────────────────────────┘
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```
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**参见**
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- [Mann–Whitney U test](https://en.wikipedia.org/wiki/Mann%E2%80%93Whitney_U_test)
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- [Stochastic ordering](https://en.wikipedia.org/wiki/Stochastic_ordering)
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