THE FLAW IN THE NRL FINALS SYSTEM

1.0. Abstract

The NRL finals system, also known as the McIntyre Final 8 System, is shown to be flawed. The flaw is exposed by a mathematical analysis of weeks 1 and 2 of the 2007 finals.

1.1. The Flaw in the McIntyre Final 8 System

The flaw, which was shown in the article titled "AN ANALYSIS OF THE FINALS SYSTEMS USED BY THE AFL AND THE NRL", does not occur every year.

The flaw is exposed in the years when the three top ranked teams all win in week 1 of the finals. The last time that happened was in 2007 when the Storm defeated the Broncos (1 v 8), the Sea Eagles defeated the Rabbitohs (2 v 7), the Cowboys defeated the Bulldogs (3 v 6) and the Warriors lost to the Eels (4 v 5).

Because of those results the only change in the ranking of the teams from week 1 to week 2 was the Warriors and the Eels swapping positions.

The following tables show the percentage chance of winning the premiership for each team in week 1 and week 2 of the finals that year.

Percentage chance of winning the premiership

2007 Week 1  Rank Team % 1 Storm 18.75 2 Sea Eagles 18.75 3 Cowboys 15.625 4 Warriors 12.5 5 Eels 12.5 6 Bulldogs 9.375 7 Rabbitohs 6.25 8 Broncos 6.25

2007 Week 2  Rank Team % 1 Storm (bye) 25 2 Sea Eagles (bye) 25 3 Cowboys 12.5 4 Eels 12.5 5 Warriors 12.5 6 Bulldogs 12.5 7 Rabbitohs 0 8 Broncos 0

The Storm and the Sea Eagles earned the bye in week 2 while the Rabbitohs and the Broncos were eliminated.

In this situation the teams ranked 3 (Cowboys), 4 (Warriors), 5 (Eels) and 6 (Bulldogs) effectively played "dead rubbers".

Even worse, the Cowboys had their chances of winning the premiership decrease from 15.625% to 12.5% even though they won. Conversely, or perversely, the Bulldogs had their chances of winning the premiership increase from 9.375% to 12.5% even though they lost.