# Mean

Checks whether the mean (average) of all the values in a column matches a given expression.

**Syntax**

`Mean`

`<COL_NAME>`

`<EXPRESSION>`

**COL_NAME**– The name of the column that you want to evaluate the data quality rule against.**Supported column types**: Byte, Decimal, Double, Float, Integer, Long, Short**EXPRESSION**– An expression to run against the rule type response in order to produce a Boolean value. For more information, see Expressions.

**Example: Average value**

The following example rule checks whether the average of all of the values in a column exceeds a threshold.

`Mean "Star_Rating" > 3 Mean "Salary" < 6200 where "Customer_ID < 10"`

**Sample dynamic rules**

`Mean "colA" > avg(last(10)) + std(last(2))`

`Mean "colA" between min(last(5)) - 1 and max(last(5)) + 1`

**Null behavior**

The `Mean`

rule will ignore rows with `NULL`

values in the calculation of the mean. For example:

`+---+-----------+ |id |units | +---+-----------+ |100|0 | |101|null | |102|20 | |103|null | |104|40 | +---+-----------+`

The mean of column `units`

will be (0 + 20 + 40) / 3 = 20. Rows 101 and 103 are not considered in this calculation.