#### Population

- PopulationVariance(a[ ])
- PopulationVariance(DBField field)
- PopulationVariance(DBField field, String groupby)

This function computes the population variance of the values referred to by the argument.

Parameters

- a - A Number array.
- field - Values of a DBField or formula field.
- groupby - A constant string to indicate the DBField, formula or parameter grouped by.

Return value

Returns a Number type value.

Examples

- `PopulationVariance([ 2.5, 4.75, 2.36, 1.25 ])`
- `Number x = PopulationVariance([1.0, 2.0, 3.0, 4.5, 45.0, 67.0])`
- `Number x[6] = [1.0, 2.0, 3.0, 4.5, 45.0, 67.0];
  Number y = PopulationVariance(x)`
- `Number x = PopulationVariance(@dbfield)`
- `Number x = PopulationVariance(@formula)`
- `Number x = PopulationVariance(@dbfield, @dbfield_groupby)`
- `Number x = PopulationVariance(@dbfield, @formula_groupby)`
- `Number x = PopulationVariance(@dbfield, @parameter)`

Note: If a field is assigned to a variable, for example x, the variable x will lose the characteristic of representing a group of values. Therefore, the following formula will be treated as incorrect.

`Number x = @dbfield;
Number y = PopulationVariance(x); // system will prompt you that there is no such kind of function.`

- PopulationStdDev(a[ ])
- PopulationStdDev(DBField field)
- PopulationStdDev(DBField field, String groupby)

This function computes the population standard deviation of the values referred to by the argument.

Parameters

- a - A Number array.
- field - Values of a DBField or formula field.
- groupby - A constant string to indicate the DBField, formula or parameter grouped by.

Return value

Returns a Number type value.

Examples

- `Number x = PopulationStdDev([1.0, 2.0, 3.0, 4.5, 45.0, 67.0])`
- `Number x[6] = [1.0, 2.0, 3.0, 4.5, 45.0, 67.0];
  Number y = PopulationStdDev( x)`
- `Number x = PopulationStdDev(@dbfield)`
- `Number x = PopulationStdDev(@formula)`
- `Number x = PopulationStdDev(@dbfield, @dbfield1)`
- `Number x = PopulationStdDev(@dbfield, @"group_field")`
- `Number x = PopulationStdDev(@dbfield, @parameter)`

Note: If a field is assigned to a variable, for example x, the variable x will lose the characteristic of representing a group of values. Therefore, the following formula will be treated as incorrect.

`Number x = @dbfield;
Number y = PopulationStdDev(x); // system will prompt you that there is no such kind of function.`