You can find out from the Leonardo Centre at the University of Sheffield which specializes in research and development in Tribology and surface engineering.
Tribology is the science of interacting surfaces and covers all aspects of friction, lubrication and wear.
The study concludes that in regards to slip hazard - "A dry banana skin is probably ok, definitely don't step on any wet banana skins. But perhaps best of all deposit you banana skins in the rubbish bin."
I'd add that if you are a really bad housekeeper at least pick up the banana peels out of the tub or shower.