From: utzoo!decvax!harpo!eagle!karn
Newsgroups: net.singles
Title: Birth control effectiveness
Article-I.D.: eagle.877
Posted: Fri Apr  8 01:52:03 1983
Received: Fri Apr  8 04:56:29 1983

With the publicity about the new "sponge" birth control device, I'm again
hearing figures given as the "effectiveness rate" for various birth
control devices.  Exactly what do these figures mean? Does an "85%
effectiveness rate" mean a 15% chance of pregnancy after one use, or
after 100, or what?  The reports never say, although I'm sure there must
be some standard definition.

Without some statement as to how the numbers are measured, such claims
are about as meaningful as "50% better than the leading brand".

Phil