I'm going to let Lou answer that one.

>> Actually if you give your old answer you have been correct.

[LAUGH]

>> I see this week is going to be hard for me.

>> So this week we're going to actually look at probability.

We're going to think about these kinds of questions

and we're going to apply it to simple games.

Our probability transcends games, obviously, right?

Lou, do you want to give us some examples of

where we might actually use probability in a more practical setting?

>> Sure.

Actually, this seemingly useless exercise we just did here is actually, it can

illustrate a very important concept, which is the use of DNA profiling in forensics.

So, just imagine a scenario where we have a crime,

and there's a suspect, and there were witnesses to that.

And then the witness comes and says something about the suspect.

And let's avoid the usual DNA for now and let's use some tricks.

But the suspect says I saw that, that the

witness says I saw that the suspect has blue eyes.

Now, we bring the suspect and suppose the suspect has blue eyes.

Now, we say, okay, it seems that the guy who actually committed the crime.

But the question now, what is the probability that we

will just get someone with the blue eyes just by chance.

So now if we imagine that the population of the world

is, has blue, green, brown, and black eyes of equal numbers.

Then if you just choose one person at random, the probability

that that person will have blue eyes is just one quarter.

So now that's not a very reliable test.

But suppose now, the witness comes and say,

the person had blue eyes and blond hair.

And let's assume that these two things have nothing to do with each other.

And again, let's assume that the world population has blond

hair, black, and brown, one 3rd, one 3rd, one 3rd.

So, now what is the probability that the person has blue eyes, and blonde hair?

So, now it becomes one 4th, times one 3rd.

So, now we stat narrowing down the options that the person has two traits by chance.

And, this is basically the idea behind, the use of DNA profiling in forensics.

That now you take a, a sample, from, from the crime scene, and you look at the DNA

of the suspect, and you look at multiple genes in the sample and in the suspect.

And now you ask the question what is the probability

that we will see such a match between the two.

And the larger the number of genes you have, and

the higher the, the match among these genes, the lower

the probability that you will see something like that by

chance, and this is how this kind of test is used.

And this is a very important example of

the use of probability in real, world situations.

>> So this week, we're going to just look at games

like this, but we want you to keep this in mind.

This goes way beyond games.

There's a lot of interesting applications of probability in computer science.