Step four: see the error

Two numbers are now sitting next to each other.

The guess: 12 dollars. The correct price: 22 dollars.

Subtract one from the other and you get the fourth step:

22 - 12 = 10

The guess was 10 dollars too low. That gap is the error, the thing named several slides ago.

This is a bad guess. It should be. The model has never seen a bottle of wine in its life, and its only opinion so far is that all four tastes count the same. Being badly wrong on the first bottle is exactly what that looks like.

Two things about the error are worth noticing, and both matter later.

It has a size. Not just wrong, but wrong by 10 dollars.

It has a direction. The guess was too low, not too high.

Size and direction. That is everything one bottle has to teach, and it is all the model gets.

Which brings the loop back around to the beginning, except for one thing that has not happened yet.

Nothing inside the model has changed.