iframe-proxy | Sunbelt Computer Software

40 lines (33 loc) · 1.51 KB

"""For more information about the Binomial Distribution -

https://en.wikipedia.org/wiki/Binomial_distribution"""

from math import factorial

def binomial_distribution(successes: int, trials: int, prob: float) -> float:

"""

Return probability of k successes out of n tries, with p probability for one

success

The function uses the factorial function in order to calculate the binomial

coefficient

>>> binomial_distribution(3, 5, 0.7)

0.30870000000000003

>>> binomial_distribution (2, 4, 0.5)

0.375

"""

if successes > trials:

raise ValueError("""successes must be lower or equal to trials""")

if trials < 0 or successes < 0:

raise ValueError("the function is defined for non-negative integers")

if not isinstance(successes, int) or not isinstance(trials, int):

raise ValueError("the function is defined for non-negative integers")

if not 0 < prob < 1:

raise ValueError("prob has to be in range of 1 - 0")

probability = (prob ** successes) * ((1 - prob) ** (trials - successes))

# Calculate the binomial coefficient: n! / k!(n-k)!

coefficient = float(factorial(trials))

coefficient /= factorial(successes) * factorial(trials - successes)

return probability * coefficient

if __name__ == "__main__":

from doctest import testmod

testmod()

print("Probability of 2 successes out of 4 trails")

print("with probability of 0.75 is:", end=" ")

print(binomial_distribution(2, 4, 0.75))

Sunbelt Computer Software