NRL Projections Update – Round 8, 2017

The thing about probabilities is that people don’t deal with them intuitively very well. This very site rated the Sharks at a 79% chance of winning over the Titans. Sure enough, the Titans came up with the goods in well fought game over the reining premiers. While 79% made Cronulla heavy favourites, that means that we expected the Gold Coast to win once in every five times the game is played. Of course, we only play the game once so we can never tell how accurate this was but it’s still a lot more likely than you would naturally expect such a heavy favourite.

Over the last ten years, Euclid has predicted the outcome of the game correctly 61.5% of the time and the system has given the favourite an average chance of 61.0%, which I think means we have the probabilities dialled in pretty well – we rate an average favourite a 61% chance of the win and our favourites win 61% of the time.

So after a round with more than a few upsets, Melbourne move clear to the top of the ladder with somewhat close call over the Warriors. There’s a lot of congestion with a number of teams shuffling around with 5-3 and 4-4 records, which covers everyone from fourth to tenth. At the bottom of the ladder, the Gold Coast and Wests stepped up a gear to move clear of Newcastle but Penrith seem to be completely lost.

Round 8 Results

manly-sm Manly 20 (4-4) d canberra-sm Canberra 18 (4-4)

brisbane-sm Brisbane 25 (5-3) d souths-sm South Sydney 24 (3-5)

parramatta-sm Parramatta 18 (4-4) d penrith-sm Penrith 12 (2-6)

north qld-sm North Queensland 24 (5-3) d newcastle-sm Newcastle 12 (1-7)

gold coast titans-sm Gold Coast 16 (2-6) d cronulla-sm Cronulla 12 (5-3)

wests tigers-sm Wests Tigers 18 (3-5) d canterbury-sm Canterbury 12 (4-4)

sydney city-sm Sydney 13 (6-2) d st george illawarra-sm St George Illawarra 12 (6-2)

melbourne-sm Melbourne 20 (7-1) d warriors-sm New Zealand 14 (3-5)

[Home team in italics]

Projected Wins

The Stocky is treating the Sharks’ surprising loss fairly harshly and they’ve blown out to 2.3 win difference. Expect that gap to close down as Cronulla repair their ELO rating. Canberra is in a similar boat after a narrow loss to the very mercurial Manly. Surprisingly, both teams now have the same record of 4-4 but both Pythagoras and the Stocky expect the Raiders to eventually win a few more games than the Sea Eagles.

Sydney’s attack, meanwhile, will need to sharpen up if they hope to improve their Pythagorean expectation. After knocking off last week’s ladder leaders in the second golden point game of the round, Stocky is favouring the Roosters and projects them to finish on a reasonable rating of 1550.

Warriors and Wests remain enigmatic. The Tigers have turned some crappy form around to start looking like building momentum. The Warriors always seem to threaten but aren’t delivering wins, so we get conflicting information through the projected wins, with the Stocky giving them a better chance than Pythagoras.

rd8-2017 wins table

rd8-2017 wins graph

Collated Ladder

The beauty of the Collated Ladder is that it looks similar to the actual NRL ladder but takes into account future information, as well as the data from the past, so it’s not the same. Canberra and Cronulla are expected to outpace Sydney eventually, although it is tight, with all expecting to take fifteen wins apiece. Brisbane trails slightly (bigger wins would boost their rating and therefore the projected wins out of the Stocky) and then everyone else is bunched pretty closely behind, looking to secure the final two spots in the top eight.

rd8-2017 collated

Probabilities Matrix

Even if you think the Collated Ladder is a crock, the real benefit of this exercise comes in quantifying the chances of teams achieving (or failing to achieve) their goals.

Melbourne return to pole position for the minor premiership, leading a close group consisting of Cronulla, St George Illawarra and Sydney, which has replaced Canberra in our top four. Together, the four are about 70% chance of winning the minor premiership and 80% if you include the Raiders.

At the other end, Newcastle now have precisely zero chance of winning the minor premiership. It’s not that they technically can’t. With sixteen rounds left to play, they could go on an unbelievable winning streak and finish with seventeen wins which would net them a minor premiership if other results go their way and they have a good for-and-against. However, it is so unlikely that not once in the 10,000 simulations of the remaining season that I did to generate these numbers did it actually happen. So not just rounded down zero but zero zero chance. As the only team on 1-7, they are now more likely than not to take the wooden spoon. Everyone else is in single digits or less.

rd8-2017 probabilities

rd8-2017 minor premier

rd8-2017 finals

rd8-2017 wooden spoon

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