Syntax
NEGBINOMDIST(failures, successes, prob)
| Parameter | Description |
|---|---|
| failures | Parameter of the NEGBINOMDIST function. |
| successes | Parameter of the NEGBINOMDIST function. |
| prob | Parameter of the NEGBINOMDIST function. |
Examples
2 bad batches before 4 good ones
Formula
=NEGBINOMDIST(2, 4, 0.8)
Returns ~0.1966. With an 80% batch success rate, there is about a 19.7% chance of getting exactly 2 bad batches before producing 4 good ones.
5 misses before first hit
Formula
=NEGBINOMDIST(5, 1, 0.1)
Returns ~0.0590. With a 10% hit rate, there is about a 5.9% chance of exactly 5 misses before the first hit.
0 failures before 3 successes
Formula
=NEGBINOMDIST(0, 3, 0.7)
Returns ~0.343. The probability of three consecutive successes with no failures is 0.7^3 = 0.343.
Common Errors
#NUM!
Number_f must be >= 0, number_s must be >= 1, and probability must be between 0 and 1 exclusive of 0.
#VALUE!
Occurs when arguments are non-numeric.
Tips
No cumulative option
NEGBINOMDIST always returns the point probability (PMF). For cumulative probabilities, use NEGBINOM.DIST with cumulative=TRUE.
Use NEGBINOM.DIST instead
This is the compatibility version. Prefer NEGBINOM.DIST in new spreadsheets for the cumulative option and consistency.
Expected failures
The expected number of failures before achieving s successes is s*(1-p)/p. For s=5 and p=0.4, expect 5*0.6/0.4 = 7.5 failures on average.
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