BINOM.INV in Collabora Office: Find the Smallest Count Meeting a Probability Target
Use Collabora BINOM.INV to identify a discrete quantile and verify both sides of its cumulative threshold.
Verification status: See the evidence and test scope described in this guide. How formula examples are checked
Quick answer: =BINOM.INV(4;0.5;0.8) has independently expected result 3. Three is the smallest count whose cumulative binomial probability reaches or exceeds 0.8.
Syntax and threshold definition
=BINOM.INV(Trials; SP; Alpha)
Trials is the number of independent trials, SP the success probability for each trial, and Alpha the target cumulative probability. All three are required. The dedicated Collabora reference defines the result using “greater than or equal to,” which matters at exact cumulative boundaries.
Use whole-number nonnegative Trials and a probability SP between zero and one. The examples use Alpha strictly between zero and one. Exact native boundary handling for Alpha endpoints or fractional trial counts is not established here.
The result is a count, not a probability. It is a discrete quantile and need not be a value whose cumulative probability equals Alpha exactly.
Example 1: inspect the probability steps
For four trials with success probability 0.5, the probabilities of counts zero through four are 1/16, 4/16, 6/16, 4/16, 1/16. The cumulative probabilities are 0.0625, 0.3125, 0.6875, 0.9375, 1.
At Alpha=0.8, count two is insufficient because 0.6875<0.8. Count three reaches the target because 0.9375≥0.8. Thus =BINOM.INV(4;0.5;0.8) targets 3.
The returned count’s cumulative value is 0.9375, not 0.8. This difference is normal for a stepwise distribution and is not a rounding defect.
Example 2: verify both neighboring counts
Enter 4, 0.5, 0.8 in B2:B4. Put =BINOM.INV(B2;B3;B4) in B6. In B7 use =BINOM.DIST(B6;B2;B3;1); independent target 0.9375.
Because this example’s B6 is greater than zero, B8 can use =BINOM.DIST(B6-1;B2;B3;1), independent target 0.6875. B7 should be at least Alpha and B8 should be below it.
The second check establishes minimality. Checking only that the returned count meets the threshold would not catch a result that is unnecessarily large. For a returned count of zero, do not blindly evaluate a negative success count; handle that boundary separately.
Advanced application: test an exact step boundary
=BINOM.INV(4;0.5;0.6875) targets 2, because equality is sufficient. Raising Alpha slightly to 0.69 moves the expected result to 3.
A small change in the threshold can therefore change the output by a whole count. Do not interpolate between two integer quantiles and assume the result has the same smallest-count meaning.
Keep Alpha at its intended precision. A display that rounds 0.6875 to 0.69 should not silently replace the stored input unless that change is deliberate.
Advanced application: interpret the event correctly
The quantile answers a statement about “at most k successes” reaching a cumulative probability target. It does not directly answer “at least k successes with probability Alpha.” For the latter, translate the upper-tail event carefully using the discrete CDF and inspect the neighboring counts.
The official reference supplies =BINOM.INV(8;0.6;0.9) with result 7. It is a useful second control with a different trial probability, still under fixed independent trials with constant SP.
Errors and troubleshooting
Validate numeric probabilities and whole-number trial counts. If the result surprises you, build a small BINOM.DIST cumulative table and locate the first row reaching Alpha. This exposes mode, sign and off-by-one mistakes clearly.
The function does not test trial independence or justify using a binomial model. Exact native error displays, extreme sizes and boundary coercions were not executed for this guide.
Availability and verification
The exact function is documented in Collabora Office 26.04 desktop help. Its source snapshot was retrieved on 2026-10-13 and hash-verified for this guide on October 15, 2026. Desktop documentation is not proof of Online or mobile support.
First introduced release and last functioning version are unknown. No native Collabora or WPS run occurred. The numerical values are independent mathematical expectations; they do not certify application-specific numerical tolerances, error codes or every edge case. Formulas use English names and semicolon separators.
The dedicated help identifies the namespace COM.MICROSOFT.BINOM.INV and says this function is outside the cited OpenFormula 1.3 standard. That is a format-namespace disclosure, not evidence of identical behavior in another product. Retain the exact dotted name when checking an imported workbook.