The Excel F.DIST function returns the (left-tailed) F probability distribution — the distribution used to compare two variances in ANOVA and F-tests.
Syntax
| Argument | Description | |
|---|---|---|
x | Required | The value at which to evaluate the function (the F statistic). Must be ≥ 0. |
deg_freedom1 | Required | The numerator degrees of freedom (a positive integer). |
deg_freedom2 | Required | The denominator degrees of freedom (a positive integer). |
cumulative | Required | TRUE returns the cumulative distribution (area to the left of x); FALSE returns the probability density at x. |
How to use it
F.DIST gives the left-tailed F distribution: with cumulative = TRUE it returns the probability that an F statistic is less than or equal to x.
The two degrees-of-freedom values come from the two samples being compared: deg_freedom1 is the numerator (the variance on top of the F ratio) and deg_freedom2 is the denominator. Because the left and right tails sum to 1, F.DIST(x,d1,d2,TRUE) and F.DIST.RT(x,d1,d2) always add up to 1.
Set cumulative to FALSE to get the probability density at x instead of the cumulative area. The companion F.INV reverses the calculation, returning the x value for a given left-tail probability.
Tip: For a one-tailed F-test of “is variance 1 bigger than variance 2?”, the p-value is the right tail — use F.DIST.RT directly rather than computing 1 − F.DIST(...,TRUE).
Try it: interactive demo
Enter an F value and the two degrees of freedom to see the left-tail cumulative probability.
Practice workbook
Frequently asked questions
What is the difference between F.DIST and F.DIST.RT?
F.DIST returns the left-tailed cumulative probability (area to the left of x), while F.DIST.RT returns the right-tailed probability (area to the right). For the same inputs the two results sum to 1.What do deg_freedom1 and deg_freedom2 mean?
n−1 for each of the two samples whose variances you are comparing.How is F.DIST different from the old FDIST?
FDIST (no dot) returns the right-tailed probability and has no cumulative switch. Its modern equivalent is F.DIST.RT. F.DIST (2010+) is the new left-tailed function with a TRUE/FALSE cumulative argument.How do I find the x value for a given probability?
F.INV for a left-tail probability, or F.INV.RT for a right-tail probability. They return the F value matching the probability you supply.Master functions like this in one day
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