Returns the standard deviation of a population represented by a series of non-blank values in field.
StDevP(field{;field... })
field - any related field, repeating field, or set of non-repeating fields; or an expression that returns a field, repeating field, or set of non-repeating fields.
Parameters in curly braces { } are optional.
Data type returned 
Originated in 
FileMaker Pro 6.0 or earlier
Field can be any of the following:
a repeating field (repeatingField).
a field in matching related records specified by (table::field), whether or not these records appear in a portal.
corresponding repetitions of repeating fields in a record (repeatingField1;repeatingField2;repeatingField3), if the result is returned in a repeating field with at least the same number of repeats.
several fields in the first matching record specified by (table::field1;table::field2;...). You can include fields from different tables (table 1::field A;table 2::field B...).
A portal displays the related values 5, 6, 7, and 8 in the field Scores. StDevP(table::Scores) returns 1.11803398....
In the following examples:
StDevP(Field4) results in an error because the population standard deviation of a single number is not defined.
StDevP(Field2) returns 1.11803398... for a non-repeating field.
StDevP(Field1;Field2;Field3) returns 2.16024689..., 2.49443825..., 1.5, 2 for repeating fields.
Note  When a referenced field is a repeating field, the StDevP function returns the standard deviation of a population in the first repetition fields, then the standard deviation of a population in the second repetition fields, and so on.
Related topics 
Functions reference (category list)
Functions reference (alphabetical list)
About formulas
About functions
Defining calculation fields
Using operators in formulas