Syntax
FTEST(array1, array2)
| Parameter | Description |
|---|---|
| array1 | Parameter of the FTEST function. |
| array2 | Parameter of the FTEST function. |
Examples
Batch consistency check
Formula
=FTEST(A2:A41, B2:B41)
Returns the p-value comparing the variance of 40 measurements from batch A versus batch B. A significant result means the batches have different consistency.
Supplier quality comparison
Formula
=FTEST(C2:C26, D2:D26)
Tests whether two suppliers' products have different variability in their specifications.
Before and after process change
Formula
=FTEST(E2:E51, F2:F51)
Compares measurement variability before and after a process improvement. If p < 0.05, the change significantly affected process consistency.
Common Errors
#DIV/0!
Occurs if either dataset has zero variance (all identical values).
#N/A
Returned if either array has fewer than 2 numeric values.
Tips
Migrate to F.TEST
FTEST is the compatibility version. F.TEST is the modern replacement with identical behavior.
Assumes normality
The F-test for variances assumes the data is normally distributed. It can give misleading results with skewed or heavy-tailed data.
Interpret carefully
A high p-value (e.g., 0.7) means no evidence of different variances. A low p-value (e.g., 0.02) suggests the variances are significantly different.
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