WBBL: How Many Points Do You Need To Qualify?

There’s been a bit of talk over on Facebook (or should I say “Meta”?) about how many points you need to qualify for the knockout stages in WBBL.

15 seems to be the consensus, and it is a pretty good rule of thumb – historically no one with 15 points has yet failed to qualify; and 14 isn’t usually enough, though two teams (or rather, one team twice – Scorchers in 2015/16 and 2020/21) have qualified with 14 points.

That said, at the time of writing, it is still mathematically possible for the Hurricanes (currently 7th, on 7 points) to qualify outright on 13 points, without rained-off games or Net Run Rate, if they win their 3 remaining games and other results go their way.

The following sequence of results – WWWwwWWWWwWWwW – where “W” is a home win, and “w” is an away win (fixtures in date order) gives this final table:

Team Points
1. Heat 21
2. Scorchers 20
3. Renegades 18
4. Hurricanes 13
5. Strikers 11
6. Sixers 11
7. Stars 10
8. Thunder 8

Furthermore, 15 points isn’t a “hard” qualify either – it is mathematically possible to get as many as 20 points and still not qualify! How? Well… I’m glad you asked!

Here’s an example end-of-season table, with 5 teams level on 20 points – so one will fail to qualify on Net Run Rate.

Team Played Won Points
1. Heat 14 10 20
2. Hurricanes 14 10 20
3. Renegades 14 10 20
4. Scorchers 14 10 20
5. Sixers 14 10 20
6. Stars 14 4 8
7. Strikers 14 1 2
8. Thunder 14 1 2

(This is just an example – no shade on anyone – the teams are in alphabetical order!)

What’s happened?

The bottom two teams – Strikers and Thunder – have won the home matches between them, and lost every other game, so have one win each.

Stars have beaten Strikers and Thunder twice each, but lost every other game, so have four wins.

Everyone else has beaten Strikers, Thunder and Stars twice (so a “base” of six wins) and then has won all their home games versus each other, giving them an additional four wins, to take them all to 20 points.

Of course, this is unlikely – the odds on the exact scenario described above are 523,347,633,027,360,537,213,511,521 (523 septillion) to 1 against, though there are other scenarios which effectively produce the same outcome – e.g. everyone in the top 5 winning their away matches against each other – that alone halves the odds to… er… 261 septillion to 1 against!

But what you need to remember is that every situation is unlikely. The situation we end this season on will also have been 523 septillion to 1 against.

So to return to the Hurricanes for a moment, the chances of them qualifying on 13 points are currently in the range of about 250 thousand to 1 against… but whatever way the table ends, the chances of that were massively against that too… and yet it still happened.

It may be mind-blowing but that’s mathematics, and as Tom Lehrer once said… try as you may, you just can’t get away from mathematics!

6 thoughts on “WBBL: How Many Points Do You Need To Qualify?

  1. Apologies for being picky but when you refer to “the odds” do you really mean this. Terms such as “Odds” and “Chances” are the probability of an event occurring. For example the odds of a coin landing heads is just under one half (it can land on its edge). The alternative is combinations and that’s very different to “odds”. In the coin case there are 3 combinations but the “odds” on one of these combinations (the edge) is incredibly small).
    To bring this back to the 523,347,633,027,360,537,213,511,521 to 1 (which regardless is a very impressive calculation); has this been achieved using the probability of win/loss/tie-washout being 33% each or something else such as win/loss being 50% (certainly not the latter because the huge number is odd not even) ?

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    • It is purely mathematical – there is no attempt to weigh the likelihood of a win/loss over a ‘no result’ – so the big number is just the number of outcomes (3 in this case) to the power of the number of games (56).

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      • Now I’m going to be really really really picky. “It is purely mathematical” should read “It is purely combinatorial” – because combinatorials, odds, chances and probability are all mathematical.

        Regardless of terminology its a very interesting article. Keep ’em coming as the matches count down.

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  2. After today’s (13th Nov in Oz) matches I reckon Renegades are guaranteed top 4 and Hurricanes are out. Heat are not quite certain of top 4 because a weird set of results could leave them equal 4th.

    Do you agree ?

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