Assuming we'll take a maximum of one hit, the expected value of a hit is the sum, over all possible card values, of the expected value for sticking on the resulting number. That gives the average of:
-0.2, -0.1, 0.0, 0.3, 0.7, 0.9, 1.0, -1.0, -1.0, -1.0, -1.0, -1.0, -1.0,
which is -0.26. It's better to hit.
What about if we get an ace. Should we hit on 15?
