Web Browser, Java, Flash.
Content Quality Concerns:
While the material successfully illustrates the relationship between within- and between-group variability, one additional piece that would make the material more complete is illustrating the effect of sample size as well.
Content Quality Strengths:
The author is very clear that this applet is not a numerical calculator, but instead demonstrates the relations "among important concepts" visually. It does an excellent job of this visual representation. The material clearly illustrates how within- and between-group variability combine to change the value of the F statistic.
Ease of Use Concerns:
Changing the variability within groups with the yellow buttons is a bit awkward. It would be preferable to grab the edges of the red icons to resize them.
Ease of Use Strengths:
The applet is quite easy to use and has very clear instructions. The flash program is of very high design quality and is very visually appealing.
Potential Effectiveness Concerns:
If an instructor wants to use the material for more than just a quick in class demonstration, it will take some creativity on the part of the instructor to get students to use it effectively. There is not a great deal you can do with this applet - it has only one quick idea to get across, but it is a wonderful visualization of that idea.
Potential Effectiveness Strengths:
Students can easily "discover" the effects of small -> large within group variability on the F-statistic, and check their intuitions. The material is fairly straightforward and easy for students to understand with very little introduction.