Mythbusters is a fun TV show where they seek out common misconceptions (“is shooting fish in a barrel easy”). If they ever want to bust a myth in the world of public speaking here is a good place to start. One popular mis-used (and over-used) misconception is the Mehrabian study into the impact of words, voice and non-verbal expressions on the message being received.
If you are using the 7-38-55 rule then you should see this video:
Bert Decker has written an article I agree with on the most often mis-used statistic in presentation skill training. Namely Mehrabian research that found:
