STDEVSAMP Function
Computes the standard deviation across column values of Integer or Decimal type using the sample statistical method.
The standard deviation of a set of values attempts to measure the spread in values around the mean and is used to measure confidence in statistical results. A standard deviation of zero means that all values are the same, and a small standard deviation means that the values are closely bunched together. A high value for standard deviation indicates that the numbers are spread out widely. Standard deviation is always a positive value.
Note
This function applies to a sample of the entire population. More information is below.
Terms...
Relevant terms:
Term  Description 

Population  Population statistical functions are computed from all possible values. See https://en.wikipedia.org/wiki/Statistical_population. 
Sample  Samplebased statistical functions are computed from a subset or sample of all values. See https://en.wikipedia.org/wiki/Sampling_(statistics). These function names include Note Statistical sampling has no relationship to the samples taken within the product. When statistical functions are computed during job execution, they are applied across the entire dataset. Sample method calculations are computed at that time. 
This function is calculated across a sample of all values.
For more information on a population version of this function, see STDEV Function.
If a row contains a missing or null value, it is not factored into the calculation. If no numeric values are detected in the input column, the function returns 0
.
The square of standard deviation is variance. See VAR Function.
For a version of this function computed over a rolling window of rows, see ROLLINGSTDEV Function.
Wrangle vs. SQL: This function is part of Wrangle, a proprietary data transformation language. Wrangle is not SQL. For more information, see Wrangle Language.
Basic Usage
stdevsamp(myRating)
Output: Returns the standard deviation of the values from the myRating
column using the sample method of calculation.
Syntax and Arguments
stdevsamp(col_ref) [group:group_col_ref] [limit:limit_count]
Argument  Required?  Data Type  Description 

function_col_ref  Y  string  Name of column to which to apply the function 
For more information on the group
and limit
parameters, see Pivot Transform.
For more information on syntax standards, see Language Documentation Syntax Notes.
col_ref
Name of the column whose values you wish to use in the calculation. Column must be a numeric (Integer or Decimal) type.
Literal values are not supported as inputs.
Multiple columns and wildcards are not supported.
Usage Notes:
Required?  Data Type  Example Value 

Yes  String (column reference)  myValues 
Examples
Tip
For additional examples, see Common Tasks.
This example shows some of the statistical functions that use the sample method of computation.
Functions:
Item  Description 

STDEVSAMP Function  Computes the standard deviation across column values of Integer or Decimal type using the sample statistical method. 
VARSAMP Function  Computes the variance among all values in a column using the sample statistical method. Input column can be of Integer or Decimal. If no numeric values are detected in the input column, the function returns 
STDEVSAMPIF Function  Generates the standard deviation of values by group in a column that meet a specific condition using the sample statistical method. 
VARSAMPIF Function  Generates the variance of values by group in a column that meet a specific condition using the sample statistical method. 
ROUND Function  Rounds input value to the nearest integer. Input can be an Integer, a Decimal, a column reference, or an expression. Optional second argument can be used to specify the number of digits to which to round. 
Source:
Students took tests on three consecutive Saturdays:
Student  Date  Score 

Andrew  11/9/19  81 
Bella  11/9/19  84 
Christina  11/9/19  79 
David  11/9/19  64 
Ellen  11/9/19  61 
Fred  11/9/19  63 
Andrew  11/16/19  73 
Bella  11/16/19  88 
Christina  11/16/19  78 
David  11/16/19  67 
Ellen  11/16/19  87 
Fred  11/16/19  90 
Andrew  11/23/19  76 
Bella  11/23/19  93 
Christina  11/23/19  81 
David  11/23/19  97 
Ellen  11/23/19  97 
Fred  11/23/19  91 
Transformation:
You can use the following transformations to calculate standard deviation and variance across all dates using the sample method. Each computation has been rounded to three digits.
Transformation Name 


Parameter: Formula type  Single row formula 
Parameter: Formula  round(stdevsamp(Score), 3) 
Parameter: New column name  'stdevSamp' 
Transformation Name 


Parameter: Formula type  Single row formula 
Parameter: Formula  round(varsamp(Score), 3) 
Parameter: New column name  'varSamp' 
You can use the following to limit the previous statistical computations to the last two Saturdays of testing:
Transformation Name 


Parameter: Formula type  Single row formula 
Parameter: Formula  round(stdevsampif(Score, Date != '11\/9\/2019'), 3) 
Parameter: New column name  'stdevSampIf' 
Transformation Name 


Parameter: Formula type  Single row formula 
Parameter: Formula  round(varsampif(Score, Date != '11\/9\/2019'), 3) 
Parameter: New column name  'varSampIf' 
Results:
Student  Date  Score  varSampIf  stdevSampIf  varSamp  stdevSamp 

Andrew  11/9/19  81  94.515  9.722  131.673  11.475 
Bella  11/9/19  84  94.515  9.722  131.673  11.475 
Christina  11/9/19  79  94.515  9.722  131.673  11.475 
David  11/9/19  64  94.515  9.722  131.673  11.475 
Ellen  11/9/19  61  94.515  9.722  131.673  11.475 
Fred  11/9/19  63  94.515  9.722  131.673  11.475 
Andrew  11/16/19  73  94.515  9.722  131.673  11.475 
Bella  11/16/19  88  94.515  9.722  131.673  11.475 
Christina  11/16/19  78  94.515  9.722  131.673  11.475 
David  11/16/19  67  94.515  9.722  131.673  11.475 
Ellen  11/16/19  87  94.515  9.722  131.673  11.475 
Fred  11/16/19  90  94.515  9.722  131.673  11.475 
Andrew  11/23/19  76  94.515  9.722  131.673  11.475 
Bella  11/23/19  93  94.515  9.722  131.673  11.475 
Christina  11/23/19  81  94.515  9.722  131.673  11.475 
David  11/23/19  97  94.515  9.722  131.673  11.475 
Ellen  11/23/19  97  94.515  9.722  131.673  11.475 
Fred  11/23/19  91  94.515  9.722  131.673  11.475 