The third bottle

A cabernet with a faint apricot note. It costs 30 dollars.

Again the weights are untouched, exactly as the last bottle left them.

This time the guess comes out like this:

The guess is about 24 dollars, around 6 dollars too low.

To tell whether the earlier bottles helped, compare this bottle with itself. With all four weights still at 8, the model would have guessed only 11 dollars and 20 cents. It would have missed by nearly 19 dollars.

Now it misses by about 6. That is genuine improvement on this bottle. Different bottles can have very different errors. A fair comparison uses the same bottle before and after the weights changed.

There is a reason for the improvement. This is a cabernet with an apricot note, and the model has now met both signals. Bottle one changed the cabernet weight. Bottle two changed the apricot weight. This bottle draws on the pair of them.

So fitting bottles one at a time has left something useful behind that carries over.

Which makes what happens next more surprising than it should be.