**1. Please download the Apple Runtime for Java available for FREE at (if you already have the Apple Applet Viewer, skip to step 5):**

http://asu.info.apple.com/swupdates.nsf/artnum/n11572

**2. Once the program has downloaded, click on the the MRJ2.2.2.smi icon on your desktop.**

**3. Click on the MRJ Install icon to install the applet viewer. **

**4. Open the Apple Applet Runner Folder**

**5. Click on the Apple Applet Runner Icon**

**6. In the file menu select Open location**

**5. Copy the URL of this page and paste it into the Location box of the Applet Runner window.**

**6. Click Open. The applet may take a moment or two to load.**

**It will be worth your time, I promise!**

**NOTE: You can also save the applet in your Apple Applet Viewer Favorites if you want to access it more quickly next time. Do the following:**

**When the applet is loaded, go to the applets menu and select add applet to list.**

The **t-test** is employed when one wishes to determine if two samples have statistically different means. The t statistic is calculated as:

where the pooled variance, , is calculated as:

If **t** is less than the critical value, then the two samples have statistically different means. The **critical value** can be determined given the sample sizes, the level of significance chosen (typically *a *= 0.05), and a critical value table.

**Adjust the means, variances, and sample sizes to the right:**

Increasing the difference between the means of the samples will increase the t value; decreasing the difference will decrease the t value. Increasing the variance will decrease the t value, whereas decreasing the variance will increase the t value. Changing the population sizes will affect both the t value and the critical value.