### 20.4.20 Cumulative distribution functions

The cdf command finds the cumulative distribution function for a probability distribution.

- cdf takes one or more mandatory arguments and one optional argument.
  - distd, the name of the function that finds the distribution’s density function.
  - params, any parameters that would normally be passed to distd.
  - x, a number.
- cdf(distd,params) returns an expression for the cumulative distribution function for distd with parameters params.
- cdf(distd,params,x) returns the value of the cumulative distribution function at x.

#### Examples

cdf(normald,0,1)

erf | ⎛ ⎜ ⎜ ⎝ |
1
2
| x | √ |
2
| ⎞ ⎟ ⎟ ⎠ | +1
2

cdf(binomial,10,0.5,4)

0.376953125 |  |  |  |  |  |  |  |  |  |