Course rating, slope?

[cnl390]

I have read the definition of course rating and slope, but don't completely understand.  i.e. which course would be considered more difficult?  A 68.1 rating 108 slope or a 72 rating 125 slope.

[Hardspoon]

9 minutes ago, cnl390 said:

I have read the definition of course rating and slope, but don't completely understand.  i.e. which course would be considered more difficult?  A 68.1 rating 108 slope or a 72 rating 125 slope.

For (essentially) any golfer, the 72.0/125 course would be harder.

The first number (68.1 vs. 72) is the difficulty for a scratch golfer; higher numbers are more difficult.  The slope is a representation of how quickly the course gets more difficult for less-skilled golfers.  A 113 slope is "standard", and means that a bogey golfer is expected to take 18 more strokes than a scratch golfer.

[hilmar2k]

I don't think I've even seen a course with a slope as low as 108. I think the lowest I've ever played is a 114, and it's a ridiculously easy course...for anyone. I feel like I'm cheating when I play there. Virtually all the courses I play are ~120.

That said, Hardspoon is correct.

Edited August 1, 2016 by hilmar2k

[Hardspoon]

On 7/24/2016 at 9:02 PM, Hardspoon said:

For (essentially) any golfer, the 72.0/125 course would be harder.

So, I'm going to revise this slightly: in this case, it's harder for every single golfer, without exception.

Just for kicks, I did the math, and you'd have to be around a +30 index () for the other course to be harder...you'd be expected to shoot about a 38 on the 72.0/125 and a 39 on the 68.1/108.  Hahaha.

I just like including that caveat as a reminder that a lower slope can mean that a course is easier, for golfers who are better than scratch.

[DaveP043]

3 minutes ago, Hardspoon said:

So, I'm going to revise this slightly: in this case, it's harder for every single golfer, without exception.

Just for kicks, I did the math, and you'd have to be around a +30 index () for the other course to be harder...you'd be expected to shoot about a 38 on the 72.0/125 and a 39 on the 68.1/108.  Hahaha.

I just like including that caveat as a reminder that a lower slope can mean that a course is easier, for golfers who are better than scratch.

This came up in another thread, how slope influences handicap scoring for plus players.  I completely agree that the math works out just as you've described, but I just don't think slope is really applicable for players who have to ADD handicap strokes to their score to get a net number.

[Hardspoon]

Just now, DaveP043 said:

This came up in another thread, how slope influences handicap scoring for plus players.  I completely agree that the math works out just as you've described, but I just don't think slope is really applicable for players who have to ADD handicap strokes to their score to get a net number.

Yeah, I think I posted in that thread...saying how it makes perfect sense.  

Course difficulty is a (idealized to) a straight line - "scratch" is just an arbitrary point on that line.

[iacas]

10 minutes ago, DaveP043 said:

This came up in another thread, how slope influences handicap scoring for plus players.  I completely agree that the math works out just as you've described, but I just don't think slope is really applicable for players who have to ADD handicap strokes to their score to get a net number.

It makes plenty of sense. The shorter version is just as @Hardspoon said. We talked about that just yesterday at Five Guys, in fact… I think.

[DaveP043]

6 minutes ago, iacas said:

It makes plenty of sense. The shorter version is just as @Hardspoon said. We talked about that just yesterday at Five Guys, in fact… I think.

I guess my objection to slope for plus handicaps occurs when a player has a really good round.  Say the same guy shoots 5 under the course rating on two different courses, with slopes of 130 and 140.  His differential, for handicap posting, would be -4.35 on the 130 course, and  -4.03 on the other one.  In essence, he's posting a higher score (smaller negative differential) for a good round on a tougher (higher slope) course than he is for a similarly good score on a lower-slope course.  I don't think its a big deal, I don't see many guys at that level playing in net events, but it seems backward to me.

[Hardspoon]

15 minutes ago, DaveP043 said:

tougher (higher slope) course than he is for a similarly good score on a lower-slope course. 

There is the problem! Higher slope doesn't mean "tougher". Higher slope means "gets harder faster for worse golfers", or "gets easier faster for better golfers". That is it. Nothing more, nothing less.

If you think of it that way, it makes perfect sense.

The confusion occurs because it's "calibrated" at a level (scratch golf) that most people never reach. 

 

[DaveP043]

11 minutes ago, Hardspoon said:

There is the problem! Higher slope doesn't mean "tougher". Higher slope means "gets harder faster for worse golfers", or "gets easier faster for better golfers". That is it. Nothing more, nothing less.

If you think of it that way, it makes perfect sense.

The confusion occurs because it's "calibrated" at a level (scratch golf) that most people never reach. 

The system also supposes that two points, which invariably define a straight line, can define the variation in scoring for a large population of golfers.  We don't have nearly enough data to know if that's true   With enough data, and enough computational time, we might find that its better described by a different curve like a log-log or semi-log regression might show.  

I'm not proposing to change anything, I think the current system works pretty well, given the huge number of players using it.  Its just that for me, with at least a rudimentary understanding of both golf and math, the reasoning begins to break down when we get into scores below the course rating, the negative differentials.

 

[Hardspoon]

4 minutes ago, DaveP043 said:

The system also supposes that two points, which invariably define a straight line, can define the variation in scoring for a large population of golfers.  We don't have nearly enough data to know if that's true   With enough data, and enough computational time, we might find that its better described by a different curve like a log-log or semi-log regression might show.  

That is a fair point. I agree there is some intuitive weirdness in calculating course handicaps at the plus level, but it's the system we have, so we might as well describe it accurately.

I guess the "higher slope equals tougher" thing is a pet peeve...there is a reason that Erik entered my name into the Edel site as "John the Pedantic".  

[DaveP043]

8 minutes ago, Hardspoon said:

I guess the "higher slope equals tougher" thing is a pet peeve...there is a reason that Erik entered my name into the Edel site as "John the Pedantic".  

Well at this stage you and I have probably either bored or confused anyone who started to follow this thread.  Occasionally our quest for accuracy may serve to muddy rather than clarify.  

And to go back to the very original question, we agree that 72/125 is "harder" for ALL humans than 68/108.

Cheers

[No Mulligans]

45 minutes ago, Hardspoon said:

There is the problem! Higher slope doesn't mean "tougher". Higher slope means "gets harder faster for worse golfers", or "gets easier faster for better golfers". That is it. Nothing more, nothing less.

If you think of it that way, it makes perfect sense.

The confusion occurs because it's "calibrated" at a level (scratch golf) that most people never reach. 

 

Higher slope means "gets easier faster for better golfers".

I don't know what you mean by "easier faster".  And if I'm reading this correctly, higher slopes are easier for better golfers than lower slopes.  Or, for example a better golfer is expected to score better on a 72/140 than a 72/110.  What?  I'm very confused.

[Club Rat]

15 minutes ago, DaveP043 said:

I think the current system works pretty well,

I have struggle many years convincing members how the system creates equality.

Where I see a possible breakdown is when players move forward, they potentially and often score better.

[DaveP043]

2 minutes ago, Club Rat said:

I have struggle many years convincing members how the system creates equality.

Where I see a possible breakdown is when players move forward, they potentially and often score better.

Yeah, I think there are obviously going to be some players whose scoring from different tees doesn't conform to the way the rating system would predict.  If those same players continue to play forward tees, things will correct themselves before long.  If those same players move forward only occasionally, they could get an "unfair" advantage when they do.  Yet other players might score nearly the same from forward tees, depending on the relative strengths and weaknesses in their games.

I know that at our course, I end up with a 4 stroke handicap difference moving either forward or back a set of tees (combining the effect of course rating and slope).  I don't have enough data to support my impression, but I think that I'd score more than 4 strokes worse moving back, but less than 4 strokes better moving forward.

[cnl390]

OK, here is the reason I initially posted the question.

The courses that I play most often are 69.3  125 & 70.1  121.  Last weekend we played a course that was 68.1  108 (Palmilla Beach Resort, Port Aransas TX).  It is a links style course in the dunes with narrow fairways and not much rough.  If you missed the fairway it was impossible to find your ball (I lost 3 on the first hole) due to very, very dense vegetation and rattlesnakes.  So I (and my buddies) found this course to be much harder than the course with a higher slope.

[iacas]

2 hours ago, DaveP043 said:

I guess my objection to slope for plus handicaps occurs when a player has a really good round.  Say the same guy shoots 5 under the course rating on two different courses, with slopes of 130 and 140.  His differential, for handicap posting, would be -4.35 on the 130 course, and  -4.03 on the other one. In essence, he's posting a higher score (smaller negative differential) for a good round on a tougher (higher slope) course than he is for a similarly good score on a lower-slope course.  I don't think its a big deal, I don't see many guys at that level playing in net events, but it seems backward to me.

It's not a "tougher" course.

Scratch is an arbitrary point on the line. You're getting trapped by the math surrounding the fact that we go on the other side of zero (0).

1 hour ago, DaveP043 said:

The system also supposes that two points, which invariably define a straight line, can define the variation in scoring for a large population of golfers.

And the +1 or +2 is closer to one of those well defined points than, say, a 9 handicap who is roughly nine strokes away from either. So if anyone is going to be accurate, it's likely the scratch and bogey golfers first, and then the guys closest to those two points, and then the guys farther away, and so on.

1 hour ago, DaveP043 said:

We don't have nearly enough data to know if that's true. With enough data, and enough computational time, we might find that its better described by a different curve like a log-log or semi-log regression might show.

We might, but at the same time… don't you think that the USGA and other groups have perhaps had that time, and the computational power, to do so?

And even if you found that a very small curve was a better fit, do you want people trying to do that math over simple "handicap index * course rating/113"? What you might give up in accuracy you likely more than gain in simplicity.

1 hour ago, DaveP043 said:

I'm not proposing to change anything, I think the current system works pretty well, given the huge number of players using it.  Its just that for me, with at least a rudimentary understanding of both golf and math, the reasoning begins to break down when we get into scores below the course rating, the negative differentials.

You're still thinking about this incorrectly, though.

Let's imagine a 72.0/80 course and a 72.0/150 slope course. A scratch golfer is going to play a 3.2 index golfer, who will get either 2 strokes or 4 strokes. He'll get more strokes on the "tougher" (your words) course, or the course that "scales faster" if you want to think of it that way.

That makes sense, right?

But now that scratch golfer takes on a +3.2 index. The +3.2 index is going to have a course handicap of either +4 or +2… but the +2 will be on the 72.0/80 course. Right?

Which makes sense, because on which course does the worse golfer need the most strokes? On the 72.0/80 or on the 72.0/150 course? They need more strokes (relatively) on the 72.0/150 because that course "scales faster."

58 minutes ago, No Mulligans said:

Higher slope means "gets easier faster for better golfers".

I don't know what you mean by "easier faster".  And if I'm reading this correctly, higher slopes are easier for better golfers than lower slopes.  Or, for example a better golfer is expected to score better on a 72/140 than a 72/110.  What?  I'm very confused.

I don't know about "gets easier faster." I think people just get tripped up by the fact that scratch is a "0."

Try it this way. Let's imagine that we factor in the course rating to a handicap index to remove the "0" point in the line. I'll make things simpler, but keep the 72.0/80 and 72.0/150 course ratings. Let's imagine the scratch golfer (new handicap index is 72.0) plays a 5 handicapper (77.0 HI) and a +5 handicapper (67.0 HI).

On the 72.0/80 course, the 77.0 guy will get either ((77.0-72.0) * 80/113) = 4 strokes or ((77.0-72.0) * 150/113) = 7 strokes. The better player (scratch) will give the worse player either 4 or 7 strokes.

On the 72.0/80 course, the 67.0 guy will give either ((67.0-72.0) * 80/113) = -4 strokes or ((67.0-72.0) * 150/113) = -7 strokes. The better player (+5) will give the worse player either 4 or 7 strokes.

I think some of you guys are getting tripped up by the simple fact that you expect the line to bounce at 0, but it's just a line. It continues through the arbitrary origin. Remember, handicap index removes about 72.0 strokes, but the handicap and slope work because the worse player always gets more strokes (before rounding) on the course with a higher slope. This is true even if either (or both) of the players is a + handicap himself.

(Consider how many strokes a +18 would have to give a +9 handicap, if either were possible… the +9 would need more strokes on the course with the higher slope… just as an 18 would need more strokes from a 9 on the same two courses.)

---

I just thought of another way of thinking about this…

It's about handicapping (you versus other golfers), not about measuring your actual performance. It's always relative to someone else, and the standards are scratch and bogey golfers.

[DaveP043]

After reading all that @iacas just wrote (I didn't want to quote the whole thing), I can understand and agree with the logic, when using the negative index to calculate on-course handicaps for any kind of competition.  Where I'm still puzzling through things is in the computation in the opposite direction, in in the use of "under par"  scores in determining the index.  I'll keep noodling, and if I can explain my confusion any more clearly, I'll do it.