binomial

x=2; % Num of pollutant
n=18; % Num of samples
p=0.1; % P(sample contains pollutant)
Px1 = binopdf(x,n,p); % P(exactly 2 samples contain pollutant)
plot(0:18,binopdf(0:18,n,p));
title("BINOMIAL PROBABILITY DISTRIBUTION");
xlabel('Number of Pollutants --->');
ylabel('Probability --->')
Px2 = binocdf(3,n,p);
r = 1-Px2; % P(at least 4 samples contain pollutant)