Negative Binomial Expected Trials

Problem

For a negative binomial distribution that counts the number of trials until r successes, with success probability p, the expected number of trials is r / p. Return 0.0 when r < 1 or p is outside (0, 1].

Hint

Each success takes a geometric number of trials, so multiply the mean by r.

Test cases

case 1

in: [3,0.5]

expected: 6

case 2

in: [5,0.2]

expected: 25

case 3

in: [1,0.25]

expected: 4

case 4

in: [0,0.5]

expected: 0

case 5

in: [2,0]

expected: 0

Starter codePython

def negative_binomial_expected_trials(r, p):
    # Your code here
    pass

5 test cases · run your code against them in the editor