The volatile nature of PGA National

Regression analysis

Four holes, four different setups. In some cases, such as No. 16, the dramatically different scoring results appear to have been prompted by the flag change. Yet in others, No. 2 notably, that’s not a plausible explanation.

What does make a course such as PGA National play so differently in benign weather from one day to another? Flag moves almost certainly play a part. But an equal part probably has to do with factors we do not yet fully comprehend.

The one clear point is that such factors exist. An excellent way to calculate their existence, if not their source, is by the use of a mathematical formula known as regression analysis. It’s designed to ascertain the strength of relationship between two sets of data…in our case a player’s performance on any given hole and that same player’s eventual score for the round.

A result of 1.0 indicates an absolute relationship, a score of 0.0 indicates no relationship whatsoever.

Over two days in similar conditions on the same course, we would expect regression analysis to produce roughly similar results for the same hole both days. But that was not at all the case at PGA National. Here’s a table of the Saturday and Sunday regression numbers, along with the difference, for all 18 holes. Pay particular attention to the final column, which shows the day-to-day swing.

Hole     Saturday     Sunday    Difference

1             .20                .19            -.01

2              .17               .38              .21

3              .18               .26              .08

4              .19               .18            -.01

5              .26               .06            -.20

6              .36               .30            -.06

7              .24               .16            -.08

8              .07               .10              .03

9              .09               .17              .08

10            .27               .07               .20

11            .17               .39               .22

12            .26               .14             -.12

13            .27               .17               .10

14            .15               .20               .05

15            .18               .41               .23

16            .26               .09               .17

17            .42               .22               .20

18            .27               .11               .16

Ten of the 18 holes at PGA National yielded performance swings exceeding 10 percent between Saturday and Sunday, and on six of those 10 holes, the swings exceeded 20 percent. That’s roller-coaster level day-to-day uncertainty.

I haven’t run similar data for the full Tour, but one must suspect that few courses are as naturally volatile as PGA National. And that’s without torrents of rain.