Now as you can see, we have 
three prediction rules,

and the first question is 
what are the three predictions

that they give for this week.

So, prediction 1, attendance last week,

well we can see that that 
attendance last week was 40,

and the prediction is 40,

so all of these actually have the 
correct answer for prediction 1.

The second one is 100 minus 
attendance last week - 60.

100 - 40

And then 20 plus attendance last week,
20 + 40 is 60

so that shows us that answer A 
is the correct one.

Now notice that none of these strategies

used this data of the attendance 
two weeks ago.

They don't have to, even though 
it is available to them,

they don't have to use it.

Now let's go to question 2.

This asks what did the three 
prediction rules say last week.

So last week, the attendance we see was 40
but before we even knew that,

we wanted to know what the 
prediction rules predict.

So prediction 1 says attendance 
last week,well that would have been 70

because it was the week 
before we're predicting.

So prediction 1 is 70

prediction 2 is 100 minus attendance
last week. 100 - 70 is 30.

And prediction 3 is 20 plus attendance
last week. 20 + 70 is 90.

So the correct answer is C.

So now we want to know which strategy 
is the current best.

And that was defined as the one that was
closest to predicting correctly last week.

Last week the real answer was 40,
and the closest prediction to 40,

well, 30 is closer to 40 than 90 or 70,

so prediction 2 gives us 
the best prediction,

and that's the one we're going 
to use this week.

Prediction 2 for this week was 60.

Well that's just at the threshold

and we said the rule was

if you are at the threshold,
or below, then you go.

So our answer is to go.