Petra;

The purpose in evaluation is to evaluate the prediction as it is made.

Don's prediction was for a 35 km radius circle. Anything inside the circle would be a hit so giving extra credit if it happens to be closer to the center isn't fair.

Suppose he used a 1000 km circle. Many quakes would fit, guaranteeing a hit. Should he get credit for a better prediction if the closest was 10 km?

Roger