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Statistical function
T.TEST
Returns the probability associated with a t-test comparing two samples.
When to use it
The p-value from a Student t-test comparing two samples. Tails 1 or 2; type 1 paired, 2 equal variance, 3 unequal variance (the safe default).
The shape of it
- Syntax
=T.TEST(array1, array2, tails, type)
Worked examples
Paired
=T.TEST({3,4,5,8,9},{2,3,4,6,8},2,1) → 0.0039
Paired, two-tailed. Each pair differs by about 1 with little spread, so the difference is significant.
Two independent groups
=T.TEST(A2:A31,B2:B31,2,3) → 0.043
Two independent groups, unequal variances: significant at 5%.
One tail
=T.TEST(A2:A31,B2:B31,1,3) → 0.0215
One-tailed is half the two-tailed p when the direction is as expected.
Worth knowing
- Use type 3 unless you have a reason to assume equal variances.
- Paired (type 1) needs the same number of observations in the same order.
- A p-value below 0.05 is the usual bar; report the means and the difference too.
Where it goes wrong
- #N/A when paired arrays differ in length.
- #NUM! for tails other than 1 or 2 or a type other than 1, 2, 3.
Related
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