R - Binomial Distribution

Binomial Distribution in R

The binomial distribution with size = n and prob = p has density

p(x) = choose(n, x) p^x (1-p)^(n-x)

for x = 0, …, n

where:

• R - Choose (binomial coefficient)

To find the probability of having k or less correct answers, we can plot a cumulative distribution.

plot(pbinom(0:40, size=20, prob=0.5) )
plot(pbinom(0:40, size=20, prob=0.7) )
plot(pbinom(0:40, size=40, prob=0.5) )

The (Probability|Statistics) - Binomial Distribution example of the Binomial Distribution in R

require(graphics)
dbinom(0:5, size=6, prob=0.3)

[1] 0.117649 0.302526 0.324135 0.185220 0.059535 0.010206

where:

• 0:5 is a vector representing k (the trial index)
• size is n, the number of trial
• prob is the probability of a success trial

• http://stat.ethz.ch/R-manual/R-devel/library/stats/html/Binomial.html