Mean
Binomial distribution expected value.
The expected value for a binomial random variable is
where n
is the number of trials and p
is the success probability.
Usage
var mean = require( '@stdlib/stats/base/dists/binomial/mean' );
mean( n, p )
Returns the expected value of a binomial distribution with number of trials n
and success probability p
.
var v = mean( 20, 0.1 );
// returns 2.0
v = mean( 50, 0.5 );
// returns 25.0
If provided NaN
as any argument, the function returns NaN
.
var v = mean( NaN, 0.5 );
// returns NaN
v = mean( 20, NaN );
// returns NaN
If provided a number of trials n
which is not a nonnegative integer, the function returns NaN
.
var v = mean( 1.5, 0.5 );
// returns NaN
v = mean( -2.0, 0.5 );
// returns NaN
If provided a success probability p
outside of [0,1]
, the function returns NaN
.
var v = mean( 20, -1.0 );
// returns NaN
v = mean( 20, 1.5 );
// returns NaN
Examples
var randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var mean = require( '@stdlib/stats/base/dists/binomial/mean' );
var v;
var i;
var n;
var p;
for ( i = 0; i < 10; i++ ) {
n = round( randu() * 100.0 );
p = randu();
v = mean( n, p );
console.log( 'n: %d, p: %d, E(X;n,p): %d', n, p.toFixed( 4 ), v.toFixed( 4 ) );
}