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by burgeralarm
4473 days ago
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Fortunately, probabilities for birth control methods aren't presented in this way. Generally, when an organization like Planned Parenthood says that the symptothermal method is 99.6% effective, what they really mean is: "Of 100 couples who use the symptothermal method correctly for one year, 0.4 (fewer than one) will have a pregnancy." (Source: http://www.plannedparenthood.org/health-topics/birth-control...) So after about 100 years of using this method, you've got a .4% chance of becoming pregnant. Seems like decent odds to me. |
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No, after one year you've got a 0.4% chance of being pregnant. Assuming this stays steady over 100 years, you'd have a 33% chance of being pregnant (1 - (0.996 ^ 100))
Their maths for a 1.8% failure rate over 10 years is right, it's about 15%.