Phelan wrote:Small correction: A group of 10 stones surrounding 3 points is worth (2*10)+3 to kill = 23 points.
I'm not sure I agree. When a black group (initially assumed alive) gets killed, each live black stone dies (and becomes 2 points for white); each dead white stone becomes alive (and becomes -2 points for black); all the black territory turns into white territory (-1 for black and +1 for white). That's a total point swing of 2 points per intersection the group occupies. (Count it in Chinese scoring and it becomes somehow clearer, I think.)
The slight imprecision in this is what you said about the killing stone, of course: I can't just assume a group alive and then suddenly dead. The group will initially be unsettled, and will need an extra black move to live (which is a black move inside black's own territory, so -1 point for black) or an extra white move to kill (which - when the black group is viewed as dead - is a white move inside white's own territory, so -1 point for white). So, in a simple unsettled group which needs one move to live/kill, the point swing is 2*(number of spaces the group occupies - 1).
(This was a deliberate imprecision, firstly because it only seems to be a matter of 2 points, secondly because I didn't want to try to explain it - I see that Bill did that for me, though, and he did it well.
Moreover, it's the rule of thumb I use in real games. Because nothing is ever a matter of one or two points in 4 kyu games!)