# F-Tests Determine if Variances are the Same or Different

## You Don't Have to be a Statistician to do an F-Test in Excel

### QI Macros Add-in for Excel Makes F-Tests as Easy as 1-2-3

- Click and drag over your data to select it in Excel:
- click on the QI Macros Menu > Statistical Tools > F & t Tests, and then select "F-test: Two-sample for Variance":
- QI Macros will prompt for a significance level (default = 0.05):
- QI Macros will perform the F-Test calculations and interpret the results for you:

**What's Cool about QI Macros F-Test?**

**Interprets the Results for You:** QI Macros compares the p value to alpha and tells you what that means. In the above example, QI Macros tells you "Cannot Reject the Null Hypothesis because p > 0.05 (Variances are the Same).

**Interactive Results**: QI Macros lets you change the significance level to see what impact those changes have on your results.

Based on the F-test results we now know which two sample t-test to run.

### F-Test Video Example

If you're producing rubber made with two different recipes, you might want to know if the variances in tensile strengths are the same or different (Juran's QC Handbook 4th pg 23.74):

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