NEGBINOMDIST(num_fail, num_success, [probability])
- num_fail - The number of unsuccessful tests.
- num_success - The number of successful tests.
- probability - The probability of the success of an attempt.
NEGBINOMDIST(10,5,0.5) returns a value of 0.03054
- NEGBINOMDIST returns the probability that there will be num_fail failures before num_success successes, when the constant probability of a success is probability.