FDIST in WPS Spreadsheet: F-Distribution Right-Tail Probability
Evaluate an F right tail with numerator and denominator degrees of freedom, verify closed-form cases and separate distribution evaluation from a complete test.
Verification status: See the evidence and test scope described in this guide. How formula examples are checked
FDIST returns P(F>x), the right-tail probability for an F distribution with specified numerator and denominator degrees of freedom. It does not calculate a variance ratio from two datasets for you. The ratio or other statistic and its degrees of freedom must already be supplied.
Syntax and argument order
=FDIST(x, degrees_freedom1, degrees_freedom2)
Degrees_freedom1 belongs to the numerator and degrees_freedom2 to the denominator. Their order matters. Original examples use positive x and small positive integer degrees of freedom. The WPS formal equation explicitly specifies the right tail; no similarly named modern function is assumed to share this contract.
If an F statistic comes from a ratio of independently estimated variances under a suitable normal model, the associated degrees of freedom need to follow that derivation. The function cannot establish independence, normality or the appropriateness of a test.
Original closed-form example
For numerator and denominator degrees of freedom both equal to 2, the right-tail formula simplifies to 1/(1+x).
- Enter 3 in A2, 2 in B2 and 2 in C2.
- Use
=FDIST(A2,B2,C2)in D2. - Independently calculate 1/(1+3)=0.25.
The complementary lower-tail probability is 0.75. Increasing x to 9 would reduce the right tail to 0.1, rather than increase it.
Independent controls
| Formula | Expected right-tail probability |
|---|---|
=FDIST(1,2,2) |
1/2 |
=FDIST(3,2,2) |
1/4 |
=FDIST(0.5,2,2) |
2/3 |
=FDIST(2,2,4) |
1/4 |
=FDIST(4,2,4) |
1/9 |
=FDIST(1,4,2) |
5/9 |
For degrees (2,4), survival is (1+x/2)^−2. For degrees (4,2), it is 1−(2x/(1+2x))^2. These elementary cases independently check that switching degrees can change a result.
Derive an interval and inspect the tail
For degrees (2,2), the probability between x=1 and x=3 is survival(1) minus survival(3), or 0.5−0.25=0.25. This subtraction order follows from using a right-tail function. Subtracting in the opposite order would produce an invalid negative interval probability.
In a statistical application, a p-value is conditional on a specified null model. It is not the probability that two population variances are equal. The source’s general discussion of comparing variation should therefore be read as an application context, not an automatic decision or proof of a difference.
Official example and limits
The vendor walkthrough uses x=17 with numerator degrees 5 and denominator degrees 2, displaying approximately 0.056484188. The function dialog and formal text preserve the same argument order and right-tail interpretation.
The lesson documents #VALUE! for nonnumeric inputs, #NUM! for negative x or degrees outside its stated range, and truncation of fractional degrees. These original controls avoid those boundaries, extreme tails and malformed inputs. Their precision is an independent reference, not a guarantee of WPS’s stored digits.
For a different nonnegative statistic distribution, see CHIDIST; a chi-square tail has a different model and parameter contract. VARP calculates a population variance rather than a distribution-tail probability.
Availability and evidence scope
The official WPS lesson is dated 2019-05-06 and explicitly labels WPS Office for Windows Personal. Its numeric build is unspecified. This documents the function by that date; it does not establish first introduction, the last functioning build, other-platform parity or a retirement/deprecation history.
The official lesson was rechecked on October 19, 2026. Original examples are documentation-derived independent calculations, not WPS or other spreadsheet-engine executions. Numeric reference values do not certify application precision or statistical model suitability.