Variance

Geometric distribution variance.

The variance for a geometric random variable is

upper V a r left-parenthesis upper X right-parenthesis equals StartFraction 1 minus p Over p squared EndFraction

where p is the success probability.

Usage

var variance = require( '@stdlib/math/base/dists/geometric/variance' );

variance( p )

Returns the variance of a geometric distribution with success probability p.

var v = variance( 0.1 );
// returns 9.0

v = variance( 0.5 );
// returns 1.0

If provided a success probability p outside of [0,1], the function returns NaN.

var v = variance( NaN );
// returns NaN

v = variance( 1.5 );
// returns NaN

v = variance( -1.0 );
// returns NaN

Examples

var randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var variance = require( '@stdlib/math/base/dists/geometric/variance' );

var v;
var i;
var p;

for ( i = 0; i < 10; i++ ) {
    p = randu();
    v = variance( p );
    console.log( 'p: %d, Var(X;p): %d', p.toFixed( 4 ), v.toFixed( 4 ) );
}