From: utzoo!decvax!harpo!eagle!mhtsa!alice!npoiv!hou5f!ariel!vax135!floyd!cmcl2!philabs!sdcsvax!sdccsu3!ee163hz
Newsgroups: net.singles
Title: Re: Birth control effectiveness
Article-I.D.: sdccsu3.481
Posted: Sun Apr 10 18:53:01 1983
Received: Wed Apr 13 01:13:32 1983
References: eagle.877


I'm certainly no authority, but I believe such statistics refer to the
number of conceptions to be expected.  In other words, 85% effectiveness
means she will get pregnant 15 times out of every 100 you-know-whats.

Actually, the numbers are determined over a vast sample of users, so
it really means that given 100 women, you are likely to make 15 of them
pregnant.  (In comparison, the Pill is usually considered 99% effective.)
It is always assumed that the product is used "correctly" in the first
place.  The actual effectiveness for a particular woman will no doubt
fall within some range deviated around the published factor.  This is
due to many factors such as body chemistry, sperm agressiveness, product
failure, etc.  
 
It all means that you were correct in saying you have a 15% chance of
getting her pregnant EVERY TIME.  It is a little like Russian Roulette.

KEITH PILOTTI (The Wiz) ...sdcsvax!sdccsu3:ee163hz