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2.4 KiB
2.4 KiB
slug | sidebar_position | sidebar_label |
---|---|---|
/en/sql-reference/aggregate-functions/reference/welchttest | 212 | welchTTest |
welchTTest
Applies Welch's t-test to samples from two populations.
Syntax
welchTTest([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 is assumed. Populations may have unequal variance.
Arguments
Parameters
confidence_level
— Confidence level in order to calculate confidence intervals. Float.
Returned values
Tuple with two or four elements (if the optional confidence_level
is specified)
- calculated t-statistic. Float64.
- calculated p-value. Float64.
- calculated confidence-interval-low. Float64.
- calculated confidence-interval-high. Float64.
Example
Input table:
┌─sample_data─┬─sample_index─┐
│ 20.3 │ 0 │
│ 22.1 │ 0 │
│ 21.9 │ 0 │
│ 18.9 │ 1 │
│ 20.3 │ 1 │
│ 19 │ 1 │
└─────────────┴──────────────┘
Query:
SELECT welchTTest(sample_data, sample_index) FROM welch_ttest;
Result:
┌─welchTTest(sample_data, sample_index)─────┐
│ (2.7988719532211235,0.051807360348581945) │
└───────────────────────────────────────────┘
See Also