Application.DStDev Method

Access Developer Reference

Estimates the standard deviation across a population sample in a specified set of records (a domain). .

Syntax

expression.DStDev(Expr, Domain, Criteria)

expression A variable that represents an Application object.

Parameters

Name Required/Optional Data Type Description
Expr Required String An expression that identifies the numeric field on which you want to find the standard deviation. It can be a string expression identifying a field from a table or query, or it can be an expression that performs a calculation on data in that field. In expr, you can include the name of a field in a table, a control on a form, a constant, or a function. If expr includes a function, it can be either built-in or user-defined, but not another domain aggregate or SQL aggregate function.
Domain Required String A string expression identifying the set of records that constitutes the domain. It can be a table name or a query name for a query that does not require a parameter.
Criteria Optional Variant An optional string expression used to restrict the range of data on which the DStDev function is performed. For example, criteria is often equivalent to the WHERE clause in an SQL expression, without the word WHERE. If criteria is omitted, the DStDev function evaluates expr against the entire domain. Any field that is included in criteria must also be a field in domain; otherwise, the DStDev function will return a Null.

Return Value
Variant

Remarks

For example, you could use the DStDev function in a module to calculate the standard deviation across a set of students' test scores.

If domain refers to fewer than two records or if fewer than two records satisfy criteria, the DStDev function returns a Null, indicating that a standard deviation can't be calculated.

You can use the DStDev function to specify criteria in the Criteria row of a select query. For example, you could create a query on an Orders table and a Products table to display all products for which the freight cost fell above the mean plus the standard deviation for freight cost. The Criteria row beneath the Freight field would contain the following expression:

Visual Basic for Applications
  >(DStDev("[Freight]", "Orders") + DAvg("[Freight]", "Orders"))

You can use the DStDev function in a calculated field expression of a query, or in the Update To row of an update query.

Bb148920.vs_note(en-us,office.12).gif Note
You can use the DStDev and DStDevP functions or the StDev and StDevP functions in a calculated field expression of a totals query. If you use the DStDev or DStDevP function, values are calculated before data is grouped. If you use the StDev or StDevP function, the data is grouped before values in the field expression are evaluated.

Use the DStDev function in a calculated control when you need to specify criteria to restrict the range of data on which the function is performed. For example, to display standard deviation for orders to be shipped to California, set the ControlSource property of a text box to the following expression:

Visual Basic for Applications
  =DStDev("[Freight]", "Orders", "[ShipRegion] = 'CA'")

If you simply want to find the standard deviation across all records in domain, use the StDev or StDevP function.

If the data type of the field from which expr is derived is a number, the DStDev function returns a Double data type. If you use the DStDev function in a calculated control, include a data type conversion function in the expression to improve performance.

Example

The following example returns estimates of the standard deviation for a population and a population sample for orders shipped to the United Kingdom. The domain is an Orders table. The criteria argument restricts the resulting set of records to those for which the ShipCountry value is UK.

Visual Basic for Applications
  Dim dblX As Double
Dim dblY As Double

' Sample estimate.
dblX = DStDev("[Freight]", "Orders", "[ShipCountry] = 'UK'")

' Population estimate.
dblY = DStDevP("[Freight]", "Orders", "[ShipCountry] = 'UK'")

The next example calculates the same estimates by using a variable, strCountry, in the criteria argument. Note that single quotation marks (') are included in the string expression, so that when the strings are concatenated, the string literal UK will be enclosed in single quotation marks.

Visual Basic for Applications
  Dim strCountry As String
Dim dblX As Double
Dim dblY As Double

strCountry = "UK"

dblX = DStDev("[Freight]", "Orders", _
    "[ShipCountry] = '" & strCountry & "'")

dblY = DStDevP("[Freight]", "Orders", _
    "[ShipCountry] = '" & strCountry & "'")

See Also