The Binomial Distribution is a discrete probability distribution Pp(n | N) of obtaining n successes out of N Bernoulli trails (having two possible outcomes labeled by x = 0 and x = 1. The x = 1 is success, and x = 0 is failure. Success occurs with probability p, and failure occurs with probability q as q = 1 – p.) So the binomial distribution can be written as
$$P_{p}\lgroup n\:\arrowvert\ N\rgroup=\left(\begin{array}{c}N\\ n\end{array}\right) p^{n}\lgroup1-p\rgroup^{N-n}$$
Example
#include <iostream> #include <random> using namespace std; int main(){ const int nrolls = 10000; // number of rolls const int nstars = 100; // maximum number of stars to distribute default_random_engine generator; binomial_distribution<int> distribution(9,0.5); int p[10]={}; for (int i=0; i<nrolls; ++i) { int number = distribution(generator); p[number]++; } cout << "binomial_distribution (9,0.5):" << endl; for (int i=0; i<10; ++i) cout << i << ": " << string(p[i]*nstars/nrolls,'*') << endl; }
Output
0: 1: * 2: ****** 3: *************** 4: ************************* 5: ************************ 6: **************** 7: ******* 8: * 9: