One Dial, Three Houses

A model guesses house prices in thousands of dollars. It has a single dial, $b$ , and whatever $b$ is set to gets added to every guess it makes.

With the dial at $b = 0$ , here is how it does on three houses:

house	guess	real price	guess − real price
1	$320$	$300$	$+20$
2	$440$	$450$	$-10$
3	$190$	$200$	$-10$

A teammate wants the simplest loss possible: the average of (guess − real price), with no squaring and no dropping of signs. At $b = 0$ that comes to

$\frac{20 - 10 - 10}{3} = 0$

Training is now left to turn the dial to whatever setting makes this loss as small as possible.

What does training do with the dial?

One Dial, Three Houses

Hints