ClickHouse/docs/en/sql-reference/aggregate-functions/reference/theilsu.md

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---
slug: /en/sql-reference/aggregate-functions/reference/theilsu
sidebar_position: 353
---
# theilsU
The `theilsU` function calculates the [Theil's U uncertainty coefficient](https://en.wikipedia.org/wiki/Contingency_table#Uncertainty_coefficient), a value that measures the association between two columns in a table. Its values range from 1.0 (100% negative association, or perfect inversion) to +1.0 (100% positive association, or perfect agreement). A value of 0.0 indicates the absence of association.
**Syntax**
``` sql
2023-01-10 15:40:48 +00:00
theilsU(column1, column2)
```
**Arguments**
- `column1` and `column2` are the columns to be compared
**Returned value**
- a value between -1 and 1
**Return type** is always [Float64](../../../sql-reference/data-types/float.md).
**Example**
The following two columns being compared below have a small association with each other, so the value of `theilsU` is negative:
``` sql
SELECT
theilsU(a ,b)
FROM
(
SELECT
number % 10 AS a,
number % 4 AS b
FROM
numbers(150)
);
```
Result:
```response
┌────────theilsU(a, b)─┐
│ -0.30195720557678846 │
└──────────────────────┘
```