# Two Sample t-Test Assuming Unequal Variances

## You can do t-Test in Excel using the Analysis Toolpak, but...

• Excel won't interpret your p-value for you; the QI Macros will!
• Excel can't give you a Box and Whisker chart of the two factors; the QI Macros can!

How do you determine if the variances are equal or unequal? Use an F-test to determine if the variances are equal or unequal.
If they are equal go to: Two-Sample t-Test assuming equal variances.
(The QI Macros Stat Wizard will do this for you automatically.)

### Example of a Two Sample t-Test Assuming Unequal Variances

In this example, we want to compare two types of structural steel and want to know if the strengths (in 1000 lbs/sq. in.) are the same or different. Next we conduct some tests and enter the data into Excel:

Warning: While you can run a t-Test using Excel's Data Analysis Toolpak, if you don't enter the two columns in the correct order, Excel will give you incorrect results. The QI Macros have eliminated this problem.

### How to Perform a t-Test Assuming Unequal Variances using QI Macros for Excel

1. Select the data with the mouse and click on the QI Macros Menu, Statistical Tools and then t-Test two sample assuming unequal variances:

2. The QI Macros will prompt for a significance level (default is .05):

3. Next the QI Macros will prompt for the hypothesized difference in the means (default is 0):

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The QI Macros will perform the calculations and interpret the results for you:

### What's Unique About t-Test Calculations in the QI Macros?

When you run the t-test, the QI Macros will compare the p-value (0.197) to the significance level (0.05) and interpret the results for you. Cannot Reject the Null Hypothesis because p > 0.05" and that the "Means are the same".

### Learn More...

Hypothesis Testing Quick Reference Card