FTEST

What it does

FTEST(array1, array2)

FTEST(array1,array2) returns a two-tailed F-test probability for comparing sample variances. FTEST is the compatibility spelling. It returns a probability, rather than the variance ratio statistic.

Try it

=FTEST({1,2,3},{2,3,4}) returns 1 under the current route. Both sample variances are one, so their ratio is one with equal degree counts.

Quirks

Each sample needs at least two numeric observations and a nonzero variance, otherwise #DIV/0!. Text, logical values and blanks in references are ignored; zeros count. Equal sample variances do not imply equal sample means or identical observations.

How to implement

Compute each sample variance and its count, put the larger variance in the numerator, and retain its matching degree count n-1. Evaluate the F right tail of the ratio, double it and cap at one. For the example both variances are one and both degree counts two. The current helper uses its own centered binary64 sample-variance calculation; it does not automatically inherit the separately recovered VAR.S computation tree. Tail and reduction discrepancies remain recorded.

Rust code

103 ftest "FTEST" (2, 2) [R "array1", R "array2"] |s, a, sv| {
    let x = sample(s, a, 0, sv)?;
    let y = sample(s, a, 1, sv)?;
    out(s, st::f_test_kernel(&x, &y))
}

No implementation has been published with a Handbook test suite for this function.

Version differences

No same-input comparison between named Excel builds is recorded for this function here. The documented behaviour below is not a measurement of every Excel release.

Alternatives

F.DIST.RT accepts a supplied ratio; VAR.S reports sample variance; T.TEST compares means under its selected model.

Named variants

No named variants are recorded yet.