Effectiveness of contraception

[Mutnofret]

Hi everyone! I have a weird question but maybe some one would help me solve it. Out of curiosity I am trying to figure out the reliability and effectivnes of contraception methods when there is more of them combined. If the pill on its own is 95% effective in preventing pregnancy, the pull out method is 70% effective and cervical cap is 89%, how much is the woman protected if using all three methods? I am not totally bad at math but I couldn't figure how to calculate it. Thanks anyone!

 

[Agent Smith]

99.835% protection

 

[khansaheb]

100% protection if the pill is held tightly between the knees, by the woman....

 

[BeansNRice]

Assuming independence among the 3 methods.

[imath]1 - (1-0.95)(1-0.7)(1-0.89) = 0.99835 = 99.835\%[/imath]

Re post #3, very cute. You can get 100% protection by gelding the man too!

 

[khansaheb]

Assuming independence among the 3 methods.

[imath]1 - (1-0.95)(1-0.7)(1-0.89) = 0.99835 = 99.835\%[/imath]

Re post #3, very cute. You can get 100% protection by gelding the man too!

However, "gelding tools" were not offered as options neither was hysterectomy!!

 

[Agent Smith]

Assuming independence among the 3 methods.

 

[Steven G]

Try to see the answer using two friendlier numbers like 50% and 25%.
25% is lost from one method while the 2nd method catches 50% of that. So in the end, both methods used together will work 100%- 12.5% or 87.5%.
Now, how can you use 50% and 25% to get 87.5%?
100% - (25%*50%) = 100%- ( .25*50%) = 100%- 12.5% = 85.5%.
Now, do your problem with the three numbers on your own.

 

[Agent Smith]

So few mathematicians.