Step two: guess a price

Four numbers went in. Now they have to come out as dollars.

There is only one rule, and it gets used four times.

Each unit contributes its number multiplied by its weight.

That is the whole calculation. Take it slowly, one unit at a time. Remember that every weight is currently 8, because the model has not learned anything yet.

Cabernet. The unit is 1 and the weight is 8. So 1 times 8 is 8.

Viognier. The unit is 0 and the weight is 8. So 0 times 8 is 0. Look carefully at what happened there. The weight is 8, exactly the same as cabernet's, but it made no difference at all, because there is no viognier in this bottle. Zero times anything is zero.

Plummy. The unit is 0.5 and the weight is 8. So 0.5 times 8 is 4. Half the plum taste, half the amount.

Apricotty. The unit is 0 and the weight is 8. Again 0, for the same reason as viognier.

All four together, then:

So the model guesses 12 dollars.

That is step two done. The guess is on the table.

Whether 12 dollars is anywhere near right, nobody in this chapter knows yet. The model certainly does not. It has no idea what wine costs, it only knows how to multiply and add.