Define "good data". It really does depend on your field. One of our biology professors once told us that any r^2 value above 0.5 could be considered "not bad" o

Define "good data". It really does depend on your field. One of our biology professors once told us that any r^2 value above 0.5 could be considered "not bad" on a linear regression in biology - I daresay physicists are used to rather nicer fits than these. But where you draw the line between "good" and "bad" data really is relative to your field of study, and science needs to be evaluated in that context.