Did YOU contract HIV during your last ***? Odds are greater than YOU reading this Post!

Looking at a news article on the odds of something good, bad or surprising happening to someone, I wondered what are the odds that a particular but random blog post would be read today by you or me i.e. someone in particular.

Delving deeper into the matter, I thought I should make certain assumptions about this problem before it starts to get beyond my mathematical/analytical abilities. So, the problem ended-up being a simple one to analyze, owing to the assumptions! Although, I would love to see comments deriding my analysis. And yeah, the HIV part comes in the end ;)

First, I would need a rough estimate of 'number of blog-posts made in a day' . It turned out to be easy. I found it in Technorati's quarterly State of the Blogosphere (April'07) report. In the article's summary it says, "...1.5 million posts per day."

Now, how many posts does 'that somebody, you or me' read in a day? The report says nothing about that. 5? 10? 20? Let me assume 21 posts, with no statistical backing.

So, is it 21/1.5 million? I'd not like to make matters complex but let's add another detail. If I start reading those 21 posts of mine - what 21 posts would I read? Most probably that link to each other. I assume probability of reaching a post randomly is 0. Thus, the 'Post in Question' that is to be read may or may not lie in my linked path or may lie too far ahead in my linked path and I may not reach that in those 21 posts I read.

I have 3 situations:
1. Post can not be reached as it is not in my path
2. Post can be reached as it is in my path but would not fall in 21 posts I read today
3. Post is reached

Matters can get more complicated, by taking into account that popular blogs are more linked and hence a post in them would be easier to stumble into. But, in all fairness to my intellectual abilities (excuse 1: c'mon man there is no statistical data?, excuse 2: the odds of this post being read are too low to take the pain :D), I assume that all 3 situations have equal chance of happening.

So, the proability is 1/3 * (21/1.5 million) or, 1/(1.5 million/7) .

Thus, the odds of 'You' reading 'This' post are 1 in 214,286. This link tells me that Odds of a person contracting HIV by having unprotected sex with someone who 'may or may not' have HIV are 1 in 200,000.

You have already read this post. Is it time for you to run to your doctor? Btw, you may like to take a look at coincidences when talking of large numbers here.

P.S. Please link back to the article if you want to reproduce it on your own site.

Disclaimer. The author is not claiming anything regarding process or probability of contraction of HIV/AIDS. Thus, reader is advised to take this article as a piece of humour and not medical advice.