Dennis, you're right, there are guidelines and formulas. So I probably was wrong about that. Actually, maybe the problem is that the formulas are too rigid. Maybe that's why Oakmont from the tips does not have a slope of 155, and neither apparently did Torrey Pines under U.S. Open conditions.
An objective way would be to get a whole bunch of bogey golfers to play the course, and see what they score. Course, you run into some chicken and egg issues there. But I think those could be handled statistically.
Jim - you do know each of Dennis and I actually do this, right? So you're not going to educate us about how it gets done...
It is very objective and it is all based on formula. Regarding slope, well... since you do understand that it is more or less measuring the DIFFERENCE in difficulty between scratch and bogey, why does it surprise you that neither Oakmont nor Torrey gets to 155? Each of those have such high difficulty for scratch (course rating) it would require astronomical difficulty for bogey (bogey rating) to get to 155. Oh the bogey rating will be high, for sure, as those are very tough courses and the bogey will score very high. But since the scratch scores a lot higher than most courses also, slope doesn't get that high.
Tom, for Oakmont to have a slope of 155, a 20 or so handicap who drives the ball 200 yards must shoot around 106 or 107 from the tips. That's using a course rating of 78.
From what I've read, seen and heard about Oakmont, I think a 200-yard-driving 20 handicap might shoot around 120 from the tips. Which would make the real slope (without the max cap) equal to around 226.
In that recent experiment with Romo et al. at Torrey, the 8 index shot 114 from the tips. He is a lot better than a 20 handicapper. Makes me think a true 20, who drives the ball so short that he can only hit a 370 yard hole with two excellent shots, would get demolished at these courses.
You see the same thing when the press plays ANGC right after the Masters. Scoring suggests a real slope of over 200 there.
Tiger's statement -- that a 10 handicap could not break 100 at Oakmont -- reflects the same thing. If he's right, that is.
I don't understand why slope is capped at 155. Wish I understood the adjustments better, as perhaps they explain why some real real hard courses slope at less than 155.