F.DIST.RT in Collabora Office: Calculate an F Right-Tail Probability
Use Collabora F.DIST.RT for upper-tail F probabilities, retain degree ordering and audit reciprocal-ratio transformations.
Verification status: See the evidence and test scope described in this guide. How formula examples are checked
Quick answer: =F.DIST.RT(2;5;10) has independently expected result approximately 0.164194951. It is the upper-tail probability beyond an F ratio of two with five numerator and ten denominator degrees of freedom.
Syntax and ratio direction
=F.DIST.RT(Number; DegreesFreedom1; DegreesFreedom2)
Number is the nonnegative F evaluation point. DegreesFreedom1 belongs to the numerator and DegreesFreedom2 to the denominator. All three arguments are required. RT selects the right tail; this function has no density flag.
Use positive whole-number degree counts in the ordinary examples. Swapping them usually changes the distribution. If an F statistic is defined as one variance or mean square divided by another, the degree counts must follow that same numerator/denominator order.
The output is a probability under the chosen F reference model. It does not measure the probability that two underlying variances are equal, and it does not establish whether the assumptions for a test are satisfied.
Example 1: build a simple upper-tail table
Put 0, 0.5, 1, 2, 4 in A2:A6. Enter =F.DIST.RT(A2;2;2) in B2 and fill down. Independent targets are 1, 2/3, 1/2, 1/3 and 1/5.
For two numerator and two denominator degrees, the independent right-tail expression is 1/(1+x). Put =1/(1+A2) in C2 and fill down for a mathematical check.
The tail decreases as x increases. At x=0 its mathematical value is one, since the distribution is supported on nonnegative ratios. Do not mistake this monotonic pattern for the increasing left-tail cumulative function.
Example 2: reproduce the official non-equal-degree example
=F.DIST.RT(0.8;8;12) has independent target approximately 0.614339644, matching the dedicated help.
The corresponding left-tail value from =F.DIST(0.8;8;12;1) is approximately 0.385660356. Their sum targets one. The explicit cumulative flag in the left-tail expression is important: density mode is not the complementary event.
For x=2 with degrees five and ten, the right tail is approximately 0.164194951 and the left tail approximately 0.835805049. These asymmetric-degree controls are more informative about argument order than the two-by-two table alone.
Advanced application: invert a positive ratio correctly
If F has numerator degrees d1 and denominator degrees d2, then 1/F has those degrees exchanged. Mathematically, the right-tail probability at x equals the left-tail probability at 1/x under the swapped degrees.
For x=2, d1=5 and d2=10, compare =F.DIST.RT(2;5;10) with =F.DIST(0.5;10;5;1). Both have independent target approximately 0.164194951.
This is not the same as simply swapping the degree arguments while leaving x and the tail unchanged. Keep the original ratio definition visible so the reciprocal operation can be audited.
Advanced application: verify a critical threshold
=F.INV.RT(0.05;5;10) has independently expected threshold approximately 3.325834530. Put it in F2 and evaluate =F.DIST.RT(F2;5;10) in F3; the target is 0.05.
A right-tail threshold can support a preselected test rule when the reference model is appropriate. It is not a general two-sided p-value formula. A two-sided variance comparison needs an explicit definition of both tails and the ratio orientation.
Errors and troubleshooting
Check for a nonnegative ratio and positive integer degree counts. A zero denominator in the calculation that produces the ratio is an upstream error; F.DIST.RT does not make that division valid.
For a very small upper tail, a direct right-tail function avoids the explicit subtraction 1-left_tail in the workbook. This is a numerical motivation, not a guarantee of native extreme-tail accuracy. The dedicated help does not specify all argument bounds, fractional-degree coercions or native errors. Use the stored unrounded statistic for comparisons whenever possible.
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 on October 15, 2026. Desktop documentation does not establish Online or mobile support. First introduced release and last functioning version are unknown; the dedicated source does not establish them.
No native Collabora Office run occurred. All worked values are independent mathematical expectations, not verification of native error codes or every numerical limit. Formulas use English names and semicolon separators.
The help identifies namespace COM.MICROSOFT.F.DIST.RT and places the function outside the cited OpenFormula 1.3 standard. This format disclosure does not prove identical behavior in another product.