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.

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.

`STDEVSAMP`

- computes standard deviation using the sample method. See STDEVSAMP Function.`VARSAMP`

- computes variance using the sample method. See VARSAMP Function.`STDEVSAMPIF`

- computes standard deviation based on a condition and using the sample method. See STDEVSAMPIF Function.`VARSAMPIF`

- computes standard deviation based on a condition and using the sample method. See VARSAMPIF Function.

**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 | `New formula` |
---|---|

Parameter: Formula type | `Single row formula` |

Parameter: Formula | `round(stdevsamp(Score), 3)` |

Parameter: New column name | `'stdevSamp'` |

Transformation Name | `New formula` |
---|---|

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 | `New formula` |
---|---|

Parameter: Formula type | `Single row formula` |

Parameter: Formula | `round(stdevsampif(Score, Date != '11\/9\/2019'), 3)` |

Parameter: New column name | `'stdevSampIf'` |

Transformation Name | `New formula` |
---|---|

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 |

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