BINOM.INV Function

Excel Functions › Statistical

Excel 2010+ Statistical

The Excel BINOM.INV function returns the smallest number of successes for which the cumulative binomial probability is at least a given criterion — the inverse of the cumulative binomial distribution.


Quick answer:
=BINOM.INV(10,0.5,0.75) smallest k with CDF ≥ 0.75 = 6

Syntax

=BINOM.INV(trials, probability_s, alpha)
ArgumentDescription
trialsRequiredThe number of independent trials.
probability_sRequiredThe probability of success on a single trial (0 to 1).
alphaRequiredThe criterion probability (0 to 1). BINOM.INV finds the smallest success count whose cumulative probability meets or exceeds it.

How to use it

BINOM.INV walks up the cumulative binomial distribution and returns the first number of successes k at which the running total probability reaches alpha. It is the binomial equivalent of a percentile.

=BINOM.INV(10,0.5,0.75) // smallest k with CDF ≥ 0.75 = 6
=BINOM.INV(10,0.5,0.5) // = 5

It is the inverse of BINOM.DIST(k, trials, probability_s, TRUE): given the cumulative probability, BINOM.INV hands back the success count. The result is always a whole number.

Acceptance sampling: BINOM.INV is handy for quality-control cutoffs — "how many defects must we allow before the probability of passing drops below 95%?"

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Result:

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Frequently asked questions

What does BINOM.INV return?
The smallest integer number of successes for which the cumulative binomial probability is greater than or equal to alpha. The answer is always a whole number.
How does it relate to BINOM.DIST?
It is the inverse of the cumulative form. BINOM.DIST(k,n,p,TRUE) gives a probability from a count; BINOM.INV(n,p,alpha) gives the count from a probability.
What is the alpha argument?
A target cumulative probability between 0 and 1 — often a confidence level like 0.95. BINOM.INV finds the success count at which the distribution first reaches it.
What replaced CRITBINOM?
BINOM.INV (Excel 2010+) is the modern name for the old CRITBINOM function. Both return the same critical binomial value.

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Related functions: BINOM.DIST · BINOM.DIST.RANGE · BETA.INV · NORM.INV · POISSON.DIST