# Statistical

### Correlation

Returns the Pearson coefficient of correlation of a set of number pairs –> [learn more](https://cloud.google.com/bigquery/docs/reference/standard-sql/functions-and-operators#corr)

```sql
CORR(@expression, @expression_2)
```

#### Return type

float

#### Parameters

| Name            | Type                                                                                                                                                                                                                                                   | Allowed values                                                           | Required | Placeholder (in UI) |
| --------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------ | -------- | ------------------- |
| `@expression`   | [variable](https://docs.redivis.com/reference/projects/transform-nodes/variable-creation-methods/common-elements#variable) or [literal](https://docs.redivis.com/reference/projects/transform-nodes/variable-creation-methods/common-elements#literal) | any [float](https://docs.redivis.com/reference/datasets/variables#float) | true     | -                   |
| `@expression_2` | [variable](https://docs.redivis.com/reference/projects/transform-nodes/variable-creation-methods/common-elements#variable) or [literal](https://docs.redivis.com/reference/projects/transform-nodes/variable-creation-methods/common-elements#literal) | any [float](https://docs.redivis.com/reference/datasets/variables#float) | true     | -                   |

### Covariance

Returns the covariance of a set of number pairs –> [learn more](https://cloud.google.com/bigquery/docs/reference/standard-sql/functions-and-operators#covar)

```sql
COVAR_@sample_type(@expression, @expression_2)
```

#### Return type

float

#### Parameters

| Name            | Type                                                                                                                                                                                                                                                   | Allowed values                                                           | Required | Placeholder (in UI)  |
| --------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------ | -------- | -------------------- |
| `@sample_type`  | [enum](https://docs.redivis.com/reference/projects/transform-nodes/variable-creation-methods/common-elements#enum)                                                                                                                                     | any of: `SAMP`, `POP`                                                    | false    | *(Sample (default))* |
| `@expression`   | [variable](https://docs.redivis.com/reference/projects/transform-nodes/variable-creation-methods/common-elements#variable) or [literal](https://docs.redivis.com/reference/projects/transform-nodes/variable-creation-methods/common-elements#literal) | any [float](https://docs.redivis.com/reference/datasets/variables#float) | true     | -                    |
| `@expression_2` | [variable](https://docs.redivis.com/reference/projects/transform-nodes/variable-creation-methods/common-elements#variable) or [literal](https://docs.redivis.com/reference/projects/transform-nodes/variable-creation-methods/common-elements#literal) | any [float](https://docs.redivis.com/reference/datasets/variables#float) | true     | -                    |

### Standard deviation

Returns the standard deviation of all values –> [learn more](https://cloud.google.com/bigquery/docs/reference/standard-sql/functions-and-operators#stddev)

```sql
STDDEV_@sample_type(@expression)
```

#### Return type

float

#### Parameters

| Name           | Type                                                                                                                                                                                                                                                   | Allowed values                                                           | Required | Placeholder (in UI)  |
| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------ | -------- | -------------------- |
| `@sample_type` | [enum](https://docs.redivis.com/reference/projects/transform-nodes/variable-creation-methods/common-elements#enum)                                                                                                                                     | any of: `SAMP`, `POP`                                                    | false    | *(Sample (default))* |
| `@expression`  | [variable](https://docs.redivis.com/reference/projects/transform-nodes/variable-creation-methods/common-elements#variable) or [literal](https://docs.redivis.com/reference/projects/transform-nodes/variable-creation-methods/common-elements#literal) | any [float](https://docs.redivis.com/reference/datasets/variables#float) | true     | -                    |

### Variance

Returns the variance of all values –> [learn more](https://cloud.google.com/bigquery/docs/reference/standard-sql/functions-and-operators#var)

```sql
var_@sample_type(@expression)
```

#### Return type

float

#### Parameters

| Name           | Type                                                                                                                                                                                                                                                   | Allowed values                                                           | Required | Placeholder (in UI)  |
| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------ | -------- | -------------------- |
| `@sample_type` | [enum](https://docs.redivis.com/reference/projects/transform-nodes/variable-creation-methods/common-elements#enum)                                                                                                                                     | any of: `SAMP`, `POP`                                                    | false    | *(Sample (default))* |
| `@expression`  | [variable](https://docs.redivis.com/reference/projects/transform-nodes/variable-creation-methods/common-elements#variable) or [literal](https://docs.redivis.com/reference/projects/transform-nodes/variable-creation-methods/common-elements#literal) | any [float](https://docs.redivis.com/reference/datasets/variables#float) | true     | -                    |