how many, how much???

hello again i am back
now i know that my only topic of conversation sometimes is Derren Brown, and well this is not about him but about something he writes about in his book which i found i took particular interest in and to not reference him could be considered plagiarism..... that and the fact that im secretly stalking him and want to be just like him.... in fact behind closed doors i dress up in silly little suits and draw on a ginger goatee beard and try to steal wallets off of Mitzy and Raz using my cunning!!!!

If there was a deadly virus and 1 in 10,000 people had it, (just imagine for a brief few seconds if you will) and you are terribly concerned that you may have in fact caught it (because you are melodramatic.... i neither know what that word really means or know if ive used it correctly!!!). you go to see the doctor (no this isn't a joke) who informs you that the test for this certain virus is 99% accurate, whether you have the virus or not (no medical test is ever 100% accurate). Now imagine to your shock horror the test comes back POSITIVE!!!! dun dun duuuuuun!
Now how worried should you be that you in fact have the virus?????? Read through the above once more and come to a decision on how likely it is that you have it as a percentage....do this before reading on.............



Did you come to the conclusion that it must be 99% as the test is 99% accurate??????
well you would be wrong........ you are actually about a hundred times less likely to have it then to not have it...... How? well remember that only 1 in10,000 people have the virus..... now lets say that 1million people take the test...... out of those 1million people only around 100 people are going to have the virus...... so out of that 100 people who have it, 99 will have been correctly diagnosed and been told that they have it which they do (as the test is 99% accurate). 1 of those will have been wrongly told they do not have it when they do........... But if you remember that the test is 99% accurate whether you have it or not...... out of the 1million people there will be 999,900 people who do not have the virus...... out of these people 1% of them will have been wrongly diagnosed as having the virus (test is 99% accurate) so 9,999 people will have been told they have it when in fact they dont!!! now which of the 2 groups are you more likely to be in, the group of 99 that have been correctly told they have it or the much larger group who have wrongly been told they have it??????????

It has been shown that we find it difficult to expand our thinking past a low scale, for example (if it was possible) if you fold a piece of paper in half 100 times how tall tall would it be? a house? a mountain? to the moon? in fact it would be as large as the known universe!!!!!! its hard to contemplate but this is why we are so amazed by amazing coincidences when if you look at the big picture its not that amazing. For example SOMEONE has to win the lottery and i can imagine that millions of people dream about winning or fantasize about winning so the chances are one of these people will win...... so when the person who wins it tells everyone they had a premonition of winning in a dream is it really seeing into the future? well obviously not to you and me but because there are millions of people who would have had the same 'premonitions' but will never win the lottery.... but people will truly believe they have these psychic powers because they cant understand the bigger picture.

I could really go on and on and on because i find this kind of stuff fascinating but its a bit crap writing all this stuff and not having someone to converse with about it..... thats this blogging in a nut shell for ya!
Anyway lets all hope that oneday i take my interest further by reading someone else's books on similar things so that i dont keep vomiting up Derren Brown all the time!!!

3...2...1... your back at the crossroads!!!!