2017 : Simulating the Final Ladder and Final Series After Round 17

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With just six weeks of the regular season remaining, results now tend to have larger effects on teams' ladder position probabilities and begin to restrict the range of possible ladder finishes for many teams.

This week's 50,000 simulations of the remainder of the 2017 AFL season sees:

  • seven teams' Finals chances move by more than 5% points
  • four teams' Finals chances move by more than 10% points
  • seven teams' Top 4 chances move by more than 5% points
  • three teams' Top 4 chances move by more than 10% points

(For details on the methodology I've used in the simulations, please see this blog.)

RESULTS

The charts below summarise the distribution of ladder finishes for the 18 teams from the simulations run after the current round, Round 17, and Round 16. Note that the ordering of the teams is slightly different in the two charts, reflecting improvement or deterioration in some team's expected ladder finish.

AFTER ROUND 17

AFTER ROUND 16

In terms of Final 8 chances, the big winners this week were:

  • Essendon: +20% points
  • Sydney: +12% points (up by 56% points now in the last five weeks)
  • West Coast: +8% points
  • Western Bulldogs: +6% points

The big losers were:

  • St Kilda -27% points
  • Melbourne: -14% points
  • Hawthorn: -5% points

In terms of Top 4 chances, we had as winners:

  • Port Adelaide: +9% points (up by 25% points in the last two weeks)
  • Sydney: +8% points
  • Geelong: +6% points
  • Adelaide: +5% points (up by 11% points in the last two weeks)

... and, as losers:

  • St Kilda: -14% points
  • GWS: -11% points (down by 19% points in the last two weeks)
  • Melbourne: -10% points

The latest heat maps appear below and show some firming up of the groups we've been noticing these past few weeks.

AFTER ROUND 17

AFTER ROUND 16

As things now stand, there are seven teams - the same one in each case - with chances ranging from

  • about 8.5% to 14% to finish 7th
  • about 10.5% to 15% to finish 8th
  • about 7.5% to 15% to finish 9th.

GAME IMPORTANCE

Next, let's update the game importance table. It shows, you'll recall, how each team's chances of making the finals varies depending on the result of each of the remaining games. The overall Weighted Ave Importance figure tells us the average amount by which the teams' finals chances are expected to change on the basis of the outcome of a particular game. A larger figure means that the game is expected to change teams' finals chances, on average, by a larger amount and hence is a more important game.

(For more details about the methodology and the rationale for it, again please see this blog.)

The most influential games in Round 18 are expected to be the Sydney v St Kilda, and Collingwood v West Coast clashes, though the Essendon v Kangaroos, and Melbourne v Port Adelaide matchups are assessed as being almost equally important.

NUMBER OF WINS REQUIRED

Next, an update on the analysis looking at how likely it is that a team will play Finals given that it finishes the home-and-away season on exactly 11, 11.5, or 12 wins.

Recall that these estimates, because they're based on a sample of simulations, are subject to error (as are all of those in this blog), which here is reflected in the width of the segment.

After last weeks' results, Port Adelaide's estimated probability of playing in the Finals were it to record just 11 wins fell by about 10% points, though given they're already on 10 wins, that finding is probably moot. They do, however, still have the highest estimated probability of making it with just 11 wins.

Teams' chances of playing Finals with 12 wins remain remarkably variable, ranging from a low of about 30% for Fremantle and around 40% for Hawthorn, to highs of around 90% for Port Adelaide, Sydney and Adelaide. The importance of percentage is clearly demonstrated in this chart by the ranges of estimated probabilities for teams currently on the same number of wins but with different percentages (eg Sydney (9 wins, 113 PC), Melbourne (9, 107), West Coast (9, 102), and St Kilda (9, 99)).

MOST LIKELY TOP 2s and top 4s

This week we'll look at some of the multi-spot ladder finishes, in particular the team orderings most likely for the Top 2 and Top 4 spots.

Based on the latest simulations, the most likely final Top 2 is Adelaide/ Geelong, which was the finishing order in about 21% of replicates. 

The next most likely finish was Adelaide/GWS, which occurred in about 17% of replicates, while third mostly likely was Geelong/Adelaide.

Combined, the 10 most-likely Top 2s account for just over 85% of replicates and include five teams: Adelaide, Geelong, GWS, Port Adelaide and, in just one of the 10 most-likely finishes, Richmond.

A much broader range of Top 4s is still possible according to the simulations, the 10 most likely quartets accounting for only 24% of replicates. 

Top of the list is an Adelaide/GWS/Geelong/Port Adelaide finish, this ordering appearing in about 1 replicate in 20. 

The next most likely ordering involves the same four teams but drops GWS back into 4th.

We could also look at Top 8s and the ordering of the entire 18 teams, but the range of possibilities for these is still so large that 50,000 replicates renders us incapable of estimating probabilities and ordering them with anywhere near sufficient precision and reliability. The most common Top 8 in the latest simulations, for example, appeared in only 26 of the 50,000 replicates.

We'll return to look at these and similar ladder-related events (such as the orderings for teams finishing 5th to 8th) as the season progresses and the possibilities shrink.

SIMULATIONS OF THE FINALS SERIES

So far this season the simulations have ended at the conclusion of the home and away season. Today we'll extend the simulations to include the entirety of the Finals series.

We'll use the same methodology that we've been using to simulating home and away games to simulate those in the Finals. To apply this methodology we need to determine venues for Finals contests, for which purpose I've assumed that:

  • All Victorian teams play their home Finals at the MCG
  • GWS play home Finals at Stadium Australia
  • Sydney play home Finals at the SCG
  • The Brisbane Lions play home Finals at the Gabba
  • Gold Coast play home Finals at Carrara
  • Adelaide and Port Adelaide play home finals at the Adelaide Oval
  • Fremantle and West Coast play home finals at Subiaco

Applying the methodology to the 50,000 final ladders produced by our original simulations yields the following results.

The extent of each bar provides an estimate of the probability that the team will exit at a specified week of the Finals. Geelong, for example, are about a 5% chance of exiting in an Elimination Final. The internal colouring of each bar reflects the final home-and-away ladder position of the team when it went out in a particular week.

So, for example, in those replicates where Adelaide win the Flag, over half of them come in seasons where they were projected to finish 1st in the home and away season (ie the red portion of the rightmost bar represents over one half of the height of that bar).

In the top section of the chart we use a common y-axis for all teams, which makes it harder to discern some of the details for teams with smaller Finals chances. The bottom section of the chart addresses this by representing the same data but with different y-axes for each team.

In this final chart we look at teams' chances for various Finals finishes, ignoring their home and away ladder positions (ie we focus solely on the heights of the bars in the previous chart).

We see here that, if we define the season in terms of the six events listed above, the most-likely finishes for each team are estimated to be:

  • Lose in a Preliminary Final: Port Adelaide, GWS, Geelong and Adelaide
  • Lose in an Elimination Final: Richmond and Sydney
  • Miss the Finals: all other teams