# isProbability > Test if a numeric value is a probability.
## Usage ```javascript var isProbability = require( '@stdlib/math/base/assert/is-probability' ); ``` #### isProbability( x ) Tests if a `numeric` value is a probability. ```javascript var bool = isProbability( 0.5 ); // returns true bool = isProbability( 3.14 ); // returns false bool = isProbability( NaN ); // returns false ```
## Examples ```javascript var randu = require( '@stdlib/random/base/randu' ); var isProbability = require( '@stdlib/math/base/assert/is-probability' ); var bool; var x; var i; for ( i = 0; i < 100; i++ ) { x = ( randu()*2.0 ) - 1.0; bool = isProbability( x ); console.log( '%d is %s', x, ( bool ) ? 'a probability' : 'not a probability' ); } ```