Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

Topic: Please comment on the following statistical calculation for the risk of pregnancy
Replies: 1   Last Post: Aug 16, 2013 1:19 PM

 Messages: [ Previous | Next ]
 Jeff Jefferson Posts: 1 Registered: 8/15/13
Please comment on the following statistical calculation for the risk of pregnancy
Posted: Aug 15, 2013 5:50 PM

Hi, the risk of pregnancy on the condom is 1 in 50 in perfect use, and 1 in.
6.7 in typical use. This is the yearly risk assuming 80-100 sex acts. The
risk of pregnancy on hormonal birth control pills is 1 in 333 in perfect
use, and 1 in 12.5 in typical use, again assuming 80-100 sex acts. If
combining the two types of birth control would the yearly risk be 1 in 6.7
times 1 in 12.5 = 1 in 83.75 in typical, and 1 in 50 times 1 in 333 = 1 in
16,650 in perfect, or would the yearly risk be 100 times safer than that.
For instance the per act risk on the condom must be 1 in 5,000 in perfect
and 1 in 670 in typical, times 100 acts to equal 1 in 50 and 1 in 6.7, and
likewise the per act risk on hormonal birth control pills must be 1 in
33,300 in perfect and 1 in 1,250 in typical, times 100 acts to equal 1 in
333 and 1 in 12.5. Therefore would you not multiply the two per act risks
times each other, for 5,000 times 33,300 = 166,500,000 combined perfect per
act, and 670 times 1,250 = 837,500 combined typical per act, then times 100
sex acts, and therefore bringing the yearly risk of pregnancy of using both
condoms and hormonal birth control pills, together, down to 1 in 1,665,000
in perfect use, and 1 in 8,375 in typical use.

Date Subject Author
8/15/13 Jeff Jefferson
8/16/13 Richard Ulrich