NRL Predictions for Round 23
Team Ratings for Round 23
The basic method is described on my Department home page. I have made some changes to the methodology this year, including shrinking the ratings between seasons.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.
| Current Rating | Rating at Season Start | Difference | |
|---|---|---|---|
| Rabbitohs | 11.06 | 5.82 | 5.20 |
| Cowboys | 8.75 | 6.01 | 2.70 |
| Sea Eagles | 7.80 | 9.10 | -1.30 |
| Roosters | 5.65 | 12.35 | -6.70 |
| Warriors | 5.40 | -0.72 | 6.10 |
| Storm | 3.89 | 7.64 | -3.70 |
| Broncos | 3.00 | -4.69 | 7.70 |
| Panthers | 2.18 | -2.48 | 4.70 |
| Knights | -3.05 | 5.23 | -8.30 |
| Dragons | -3.11 | -7.57 | 4.50 |
| Bulldogs | -3.78 | 2.46 | -6.20 |
| Titans | -4.79 | 1.45 | -6.20 |
| Eels | -6.28 | -18.45 | 12.20 |
| Sharks | -7.97 | 2.32 | -10.30 |
| Raiders | -8.92 | -8.99 | 0.10 |
| Wests Tigers | -11.62 | -11.26 | -0.40 |
Performance So Far
So far there have been 160 matches played, 91 of which were correctly predicted, a success rate of 56.9%.
Here are the predictions for last week’s games.
| Game | Date | Score | Prediction | Correct | |
|---|---|---|---|---|---|
| 1 | Rabbitohs vs. Sea Eagles | Aug 08 | 23 – 4 | 5.20 | TRUE |
| 2 | Broncos vs. Bulldogs | Aug 08 | 41 – 10 | 7.10 | TRUE |
| 3 | Cowboys vs. Wests Tigers | Aug 09 | 64 – 6 | 18.30 | TRUE |
| 4 | Knights vs. Storm | Aug 09 | 32 – 30 | -3.60 | FALSE |
| 5 | Eels vs. Raiders | Aug 09 | 18 – 10 | 6.90 | TRUE |
| 6 | Warriors vs. Sharks | Aug 10 | 16 – 12 | 20.90 | TRUE |
| 7 | Dragons vs. Panthers | Aug 10 | 4 – 16 | 1.80 | FALSE |
| 8 | Roosters vs. Titans | Aug 11 | 26 – 18 | 16.60 | TRUE |
Predictions for Round 23
Here are the predictions for Round 23. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.
| Game | Date | Winner | Prediction | |
|---|---|---|---|---|
| 1 | Rabbitohs vs. Broncos | Aug 14 | Rabbitohs | 12.60 |
| 2 | Eels vs. Bulldogs | Aug 15 | Eels | 2.00 |
| 3 | Raiders vs. Dragons | Aug 16 | Dragons | -1.30 |
| 4 | Storm vs. Sharks | Aug 16 | Storm | 16.40 |
| 5 | Wests Tigers vs. Roosters | Aug 16 | Roosters | -12.80 |
| 6 | Knights vs. Warriors | Aug 17 | Warriors | -4.00 |
| 7 | Titans vs. Sea Eagles | Aug 17 | Sea Eagles | -8.10 |
| 8 | Panthers vs. Cowboys | Aug 18 | Cowboys | -2.10 |
David Scott obtained a BA and PhD from the Australian National University and then commenced his university teaching career at La Trobe University in 1972. He has taught at La Trobe University, the University of Sheffield, Bond University and Colorado State University, joining the University of Auckland, based at Tamaki Campus, in mid-1995. He has been Head of Department at La Trobe University, Acting Dean and Associate Dean (Academic) at Bond University, and Associate Director of the Centre for Quality Management and Data Analysis at Bond University with responsibility for Short Courses. He was Head of the Department of Statistics in 2000, and is a past President of the New Zealand Statistical Assocation. See all posts by David Scott »
Hi – this is v interesting, glad you developed it. Seems to me that over the past few weeks the predictions have generally been right when the margin is over a lowish threshold (somewhere around the 5-7 points mark?) but mixed/wrong when the predicted margin is small. I wonder if you’ve ever looked back at the track record for predicted margins say >= 5?
10 years ago
Well that is what you would expect, to correctly predict the ones where the odds are strongly in your favour as indicated by the predicted points difference being large. So I haven’t investigated that. What I do find surprising is how often a team wins totally against the odds. Week 20 was an extreme case: the Sharks shouldn’t have beaten the Panthers and the Eels shouldn’t have beaten the Titans, but they did. The Storm away to the Broncos were very unlikely to win, but thrashed the home team.
10 years ago