Percentage effectiveness

OK, stats can be great – I like them. But sometimes they can be very unuseful. My mum was told today that she has an 8.5% chance of coronary heart disease, whilst my dad has a 22% chance… is that in their lifetime? Or this year? Or today?!

And that got me thinking about another such stat that confuses me… It’s stuff to do with contraception. (And I guess I prolly need to know this since I’ll be teaching some sex ed at school to poor 11-year-old year 7s) When a contraceptive is measured for effectiveness, e.g. 99% what does that mean? Does it mean that 99% of people NEVER get pregnant when using it? Or does it mean 99% of the time you won’t, meaning that on in every 100 sexual interludes (heh, I made that name up) would result in pregnancy with some methods (pill, coil etc). Or is it 99% of people won’t get pregnant in a year of using it… surely that depends on how many “interludes” they partake in?

I mean 99% sounds good, but it’s so subjective. On the other hand, my mum also has over-average lung size (a.k.a. a good set of pipes) and good bone density (she’s rock ‘ard!), so that’s nice 🙂

Love you Mum & Dad x

Update: I just found this which says, of the combined pill:

“This pill is 99% effective… This means that 1 in every 100 women who use [it] will get pregnant each year.”

So if I make a conservative estimate that there are 1 million sexually active women in the UK, that there are 10,000 unexpected pregnancies each year in the country?  Or if you use it for 10 years, does that mean there’s a 1 in 10 chance of getting pregnant in that time?

That’s not what I expected…

Author: Alex

I am X3JA

2 thoughts on “Percentage effectiveness”

  1. Basically, what we were taught at medical school is that – for example with a condom (which is considered 97% effective):

    If 100 couples we having sex and using a condom (exactly as it should be used and as tested in lab conditions) probability would suggest that for 3 of those 100 couples, the condom is ineffective and, therefore, there is a chance the woman could fall pregnant or that there could be tramsmission of an STI.

    So for 3% of the couples, there would be the same risks associated with unprotected sex. Of course it is highly unlikely that all 3 couples would achieve a pregnancy as there is only about a 20/30% chance of this happening with unprotected sex per female cylce and even chance less if the woman is older. If my calculations are correct, then statistically one of the 100 couples might end up pregnant (but all 3 couples could transfer an infection). Therefore condoms can be considered a very effective method of contraception if used correctly.

    In real life, however, most contraceptives are a lot less effective than they say they are. Two examples of this would be the condom and the pill. In real-life the effectiveness of a condom is probably less than 90% because people don’t use it properly (i.e. use it with the wrong kind of lubricant which can corrode the condom, or damage the condom, or, use the condom too late – it should be used at the very beginning of sexual contact).

    With the pill, it is only 99% effective if you take it exactly according to the manufacturer’s instructions i.e. never miss one, never take antibiotics at the same time, using secondary protection with suffering from a tummy bug etc…

    The most common reason for becoming pregnant while using a contraceptive is not that the contraceptive has failed, but as a result of human error when using it.

    The point I am trying to make is, if you’re teaching sex-ed, please make sure that the kids understand they have to follow the instructions to the letter in order to get maximum protection from their contraceptive method.

  2. I feel the above commentee did a good job explaining the effectiveness of sex contraception. I’d have to agree 😉

    Can I see a video of you teaching sex-ed alex?

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