Returns the Weibull distribution.
| Name | Type | Description |
| arg1 | number | The value at which to evaluate the function, a nonnegative number. |
| arg2 | number | The alpha parameter of the distribution, a positive number. |
| arg3 | number | The beta parameter of the distribution, a positive number. |
| arg4 | boolean | A logical value (true or false) that determines the function form. If it is true, the function returns the cumulative distribution function. If it is false, the function returns the probability mass function. |