Amazing application of Baye's Theorem- must read

I was wondering how these IIT guys get everything in life.
A seat in a prestigious college, an amazing career awaiting them, big money, success etc whic is common for most of the IIT'ians.

But how do they manage to date the prettiest babes?
NO. Its not always arranged marriage where its every girl's parents dream to have a son in law from an IIT.
Many get to date an awesome pretty girl while in college itself.
How do they do this? What do they have in IIT? Do they talk so well? May be not. And even if they do, come on how many non IIT'ians talk well and how many of them are able to successfully convert a stranger to a friend>> close friend>> lover>> wife?????
I mean IIT'ians have ZERO or very less failure rates.

So whats it?
Come on.. neither am i in IIT nor do i have a super girlfriend.
But i have on example to show you. The main reason for writing this post.

If a girl smiles at you, what is the probability that she likes you?
Try to answer before i give you an IIT'ian answer.

Have you heard of Baye's theorem?
Sounds familiar? Apply it here.



is what you want to know - the probability she likes you given the fact that she smiles at you.

is the probability that she will smile given that she sees someone she likes.

is the probability that she likes a random person.

is the probability that she will smile at a random person.

For example, suppose she just smiles at everyone. Then intuition says that fact that she smiles at you doesn't mean anything one way or another. Indeed, and , and we have



meaning that knowing that she smiles at you doesn't change anything.

At the other extreme, suppose she smiles at everyone she likes, and only those she likes. Then and .  Then we have



and she is certain to like you.

In the intermediate case, what you need to do is find the ratio of odds of smiling at people she likes to smiles in general, multiply by the percentage of people she likes, and there is your answer.

The more she smiles in general, the lower the chance she likes you. The more she smiles at people she likes, the better the chance. And of course the more people she likes, the better your chances are.


How did you feel reading so far?
Doesn't it seem like it is much easier to just enjoy the moment of the girl's smile and assume she likes me and continue to fantasize about her than to do all this non sense?
Hmmm true that for me.
The very reason why I am  not in IIT, why no US posting, no FIL desperately wanting me as his son in law :-)