Course Ratings and Slope, Difficulty, and Hole Stroke Index

[iacas]

2 hours ago, Carl3 said:

I was talking about the course rating, which is based on a scratch golfer and appears to be little affected by any of the obstacle calculations (less than 5%).

I've been the course rating captain for my area for fifteen years. I have attended multiple national calibration workshops, and will be certified when I wrap up my nearly hundred hours of online training (most of which is just watching basic videos 😛). I have a bit of a clue here…

You missed my point. Since the rating could be LOWER than the yardage / 220 + 40.9… you're not really talking about it the right way. What would your simple math find - that the yardage was 102% of the rating? That doesn't make sense. There are + and - adjustments. That doesn't mean that if they cancel each other out, the the distance was responsible for 100% of the course rating. Those other factors still went into the course rating.

😛

2 hours ago, Carl3 said:

The slope however is much more affected by the obstacles, which might have been what you were thinking of.

No. I wasn't. The slope is just based on the scratch and bogey rating (like the smash factor is just a result of the club and ball speed).

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Heck, @Carl3, the + 40.9 for putts and short shots is put into the rating. Using your math, a course of 7000 yards and a rating of 72.0… only gets 7000/220/72.0 = 44.2% of the rating from the "length." But that doesn't really work, either.

You're kinda doing math like this: years ago someone found that the temperature of an iPhone went from 20°C to 30°C or something, and wrote a headline about how it was "150% hotter" than previous models or something like that. The problem is that they didn't consider the scale, or the base… or they might have used Kelvin, where the increase was not 150%, but more like 3%.

Your way of measuring it as a percentage like this is nonsensical, because again you could have a course rating that is 102% of the "length" (yardage / 220 + 40.9), and as I pointed out above, the 40.9 has nothing to do with length, but is a constant, so… one could better argue (still kinda incorrectly though) that no course rating is over 50% yardage.

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Again, the truth is that the rating is highly dependent on the yardage, but… given the rough range in which we're operating, the features of the course determine a good bit more than the 1-3% you seem to think they contribute to the final rating. You're really not gonna find a 6500-yard 61-rated course, and you're not going to find a 77-rated course that short, either. So that narrows the 6500-yard courses to a smaller range (and it's really a bit smaller than even that), where the features dictate much of the differences from course to course.

Is yardage a big factor? Yes. But it's not 99% any more than it could be 102%, because that doesn't even make sense.

[Ty_Webb]

18 hours ago, iacas said:

You're kinda doing math like this: years ago someone found that the temperature of an iPhone went from 20°C to 30°C or something, and wrote a headline about how it was "150% hotter" than previous models or something like that. 

50% hotter 😜
 

(Acknowledging that you’re absolutely right about it really being more like 3% since 0 isn’t really 0)

Edited August 17, 2025 by Ty_Webb

[iacas]

1 hour ago, Ty_Webb said:

50% hotter 😜

(Acknowledging that you’re absolutely right about it really being more like 3% since 0 isn’t really 0)

Yes, sorry, I was writing quickly, but IIRC, the person also made that mistake. I think they said something like "the new iPhone [or version of iOS] runs at 150% hotter than…".

😛 

But that wasn't the point I was trying to make, and yeah, 50%. When really it's like 3%, because there's an absolute zero, and you'd really want to measure in K, not C.

[Ty_Webb]

3 hours ago, iacas said:

Yes, sorry, I was writing quickly, but IIRC, the person also made that mistake. I think they said something like "the new iPhone [or version of iOS] runs at 150% hotter than…".

😛 

But that wasn't the point I was trying to make, and yeah, 50%. When really it's like 3%, because there's an absolute zero, and you'd really want to measure in K, not C.

Funnily enough this is very similar to what trips people up about plus handicaps. 0 isn’t the real 0 in a handicapping sense because you can get (a lot) better than 0 and people think how handicaps are treated should somehow change at 0.