beta_inv()
Returns the inverse of the beta cumulative probability beta density function.
beta_inv(0.1, 10.0, 50.0)
If probability = beta_cdf(x,...), then beta_inv(probability,...) = x.
The beta distribution can be used in project planning to model probable completion times given an expected completion time and variability.
Syntax
beta_inv(probability, alpha, beta)
Arguments
- probability: A probability associated with the beta distribution.
- alpha: A parameter of the distribution.
- beta: A parameter of the distribution.
Returns
- The inverse of the beta cumulative probability density function beta_cdf()
Notes
If any argument is nonnumeric, beta_inv() returns null value.
If alpha ≤ 0 or beta ≤ 0, beta_inv() returns the null value.
If probability ≤ 0 or probability > 1, beta_inv() returns the NaN value.
Given a value for probability, beta_inv() seeks that value x such that beta_cdf(x, alpha, beta) = probability.
Examples
datatable(p:double, alpha:double, beta:double, comment:string)
[
0.1, 10.0, 20.0, "Valid input",
1.5, 10.0, 20.0, "p > 1, yields null",
0.1, double(-1.0), 20.0, "alpha is < 0, yields NaN"
]
| extend b = beta_inv(p, alpha, beta)
| p | alpha | beta | comment | b |
|---|---|---|---|---|
| 0.1 | 10 | 20 | Valid input | 0.226415022388749 |
| 1.5 | 10 | 20 | p > 1, yields null | |
| 0.1 | -1 | 20 | alpha is < 0, yields NaN | NaN |
See also
- For computing cumulative beta distribution function, see beta-cdf().
- For computing probability beta density function, see beta-pdf().