# StDev, StDevP Functions

Return estimates of the standard deviation for a population or a population sample represented as a set of values contained in a specified field on a query.

##### Syntax

**StDev(***expr***)**

**StDevP(***expr***)**

The *expr* placeholder represents a string expression identifying the field that contains the numeric data you want to evaluate or an expression that performs a calculation using the data in that field. Operands in *e**xpr* can include the name of a table field, a constant, or a function (which can be either intrinsic or user-defined but not one of the other SQL aggregate functions).

##### Remarks

The **StDevP** function evaluates a population, and the **StDev** function evaluates a population sample.

If the underlying query contains fewer than two records (or no records, for the **StDevP** function), these functions return a **Null** value (which indicates that a standard deviation cannot be calculated).

You can use the **StDev** and **StDevP** functions in a query expression. You can also use this expression in the **SQL** property of a **QueryDef** object or when creating a **Recordset** object based on an SQL query.