This applet simulates a probability tree diagram. Step 1: Click inside the appropriate box on the desired level to build the tree. Step 2: Click on "Set Probabilities" at the top. Step 3. When you enter the respective probabilities, you must hit the ENTER key after each one. Step 4: Once all of the probabilities have been set (they should be blue), click "Final Tree" Step 5: Click "Simulation".

This source defines and explains variance and standard deviation.

The applets in this section of Statistical Java address Power. Users can perform one or two tailed tests for proportions or means for one or two samples. Set the parameters and drag the mouse across the graph to see how effect size affects power. An article and an alternative source for this applet can be found at http://www.amstat.org/publications/jse/v11n3/java/power/ This page was formerly located at http://www.stat.vt.edu/~sundar/java/applets/Power.html