All language subtitles for 97031x_PR_Conditional_Prob_04_Intuition_Game_v1-en

PETER REDDIEN: Now, to help your intuition,

I thought I would do a quick game just to introduce this.

And I need a volunteer for this.

So can I get a volunteer?

So I've got three lids here.

OK, so I've got a blue lid, a green lid, and an orange lid.

STUDENT: OK.

PETER REDDIEN: All right.

So, this morning, I was thinking about how

I was going to do this.

I was talking to my daughters at the breakfast table.

And I got them to write a note--

I said I was going to do this game for the class.

Could you write a note for the class

that then we could show the class if they get it right?

But if they don't get it right, you don't get the note.

It was totally up to them to decide what

they would write to the class.

So there was some uncertainty of what they would write there.

I didn't decide.

So they did it.

OK, so those notes are now under one of these lids.

OK, so you get to try to pick the lid

it's under to see if you get it right.

So which lid do you want to pick?

STUDENT: I'll pick the green one.

PETER REDDIEN: OK, you pick the green one.

Now, don't turn it over yet.

OK, so I'm going to tell you that it is

not under the orange one, OK.

STUDENT: OK.

PETER REDDIEN: Now you can stick with the green one if you want,

or you can switch to the blue one if you prefer.

[CHATTER]

You're going to switch to the blue one.

OK, go for it.

[CHEERING AND APPLAUSE]

You got it right, OK.

[GIGGLING]

All right.

So, this was the first one.

So one of my daughters wanted to tell you that crickets

have ears on their legs.

[LAUGHTER]

I thought it was pretty interesting.

I actually looked it up.

It's true.

And then my other daughter decided-- so she

wanted to make a drawing.

And this was a drawing of me, she said.

[LAUGHTER]

So, there you go.

All right.

OK.

Very good.

Thank you.

You can head back.

[APPLAUSE]

Amanda did the right thing.

And so let me try to give you a little intuition for this,

and then you can try to calculate why yourself

as we get to the end of this lecture.

So, at the beginning, the notes were under one

of these three containers.

So there's a one third chance it was under whatever she picked,

and there was a 2/3 chance it was under one of the two

she didn't pick.

And I was giving her the chance to reveal both of those.

Because I revealed the orange one,

and then, she could switch or not to the other one.

So there was a 2/3 chance it was under the one

that she switched to.

This example could have gone badly

if she had picked the right one at the beginning

and still switched, and did the right thing,

but we got lucky as well.

And she did the right thing.

OK, so that intuition is sometimes not

immediately obvious to people, and we're

going to walk through how you figure out

these types of probabilities.

And I'll touch upon why this impacts

lots of things when we're using our intuition to assess

probability of events.