re: #239 GeneJockey

Because for the most part they work against conception. First, it’s only 40% of this small sample that are positive, so the numbers in the population as a whole might be smaller. Second, the ones that were positive were not very positive, i.e. the numbers were very low, even when present. Third, not all the positives contained healthy, motile sperm. Fourth, the volume of preejaculate is generally less than ejaculate. The study points out that the number of sperm found even in the samples with the highest sperm count would be considered barely fertile if that were for ejaculate, and associated with less than a 2.5% chance of pregnancy within a year of trying.

So, you have a fraction of a fraction of the population, producing small volumes of fluid with very low numbers of sperm.

Okay, then consider what percentage of the population practices coitus interruptus as their sole contraception - a small percentage. Consider what percentage of those do it consistently correct. Consider what percentage of those are having intercourse on a regular basis.

You’re looking at fractions of fractions of fractions of fractions, and all with low probability.

I’m sorry, but we’re comparing rations, not sheer numbers. So how much of a fraction is doesn’t matter, unless you’re saying it’s so low that it’s statistically meaningless.

And the first section would definitely be an adequate description, but it would tend to back up the idea that coitus interruptus, if used perfectly, is a good form of birth control.