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What's your chance of getting an Australium? - stats.tf edition

cares

By cares
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cares Newbie

cares

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tl;dr below (in a spoiler).

 

Australium drop chance is a mystery, Gaben hasn't written it anywhere public and it's unlikely he ever will. Let alone pans, although those are easy to calculate relative to australiums. So how do we get an estimate? Well, it's hard. But we have stats.tf, so let's use that.

 

Robot parts and hats drops are very unpredictable, it's enough of a feat to figure that out, not to mention a tour has 4 stages, so it's completely unreliable. So for the purpose of simplicity, we use Fabricators (http://stats.tf/item/20002/Fabricator + http://stats.tf/item/20003/Fabricator) and Killstreak Kits (http://backpack.tf/stats/Unique/Kit/Tradable/Craftable - only use the "MvM Badge completion reward" slice), assuming a drop rate of 2 per tour. From what I've seen you still get 2-ish kits/fabricators ("KF") alongside a possible australium. I think most people would agree with me that 2 kits/fabricators is the most common drop.

 

stats.tf never "forgets" items. That means, if an itemid is no longer in any of the indexed backpacks, it is not removed from the database as it might have been traded away to an unindexed backpack, and who knows, what if it's in a backpack which needs to be rescanned (stats.tf currently does not crawl backpacks periodically, only on demand). There's really no way of knowing. If a fabricator was crafted/kit was used before a backpack was indexed, stats.tf will never know about it. A bit unfortunate, but that's the harsh truth. Fortunately, most australiums were, when they dropped, in commonly updated backpacks, making it unlikely the kits/fabricators obtained from tours have never been indexed. And the person who got it was most likely more busy trying to sell it or admire it than using their KFs. That's good.

 

backpack.tf is nice enough to combine the two types of fabricators in its statistics, Spec and Prof KS fabricators. So we use that for a bit of convenience: http://backpack.tf/stats/Unique/Fabricator/Tradable/Craftable

And for kits we strictly use the MvM Badge completion reward slice (really nice Valve added this): http://backpack.tf/stats/Unique/Kit/Tradable/Craftable

 

Currently that is 213147 (116488 + 96659) stats.tf has ever known about. That's KFT = 106574 (rounded up) ToD tickets which had to bite the dust, or so. Now, onto australiums. We'll add up the australium counts and deduct that count * 2 from KFT, creating a new variable KFP. We do this because we assume we always get 2 KF along with an australium.

 

Stats (as of right now):























 

AusT = 40 + 139 + 134 + 35 + 148 + 141 + 113 + 129 + 149 + 130 + 129 + 168 + 190 + 149 + 170 + 167 + 156 + 178 + 151 + 181

     = 2797

 

KFP = KFT - AusT * 2

     = 100980

 

Now, the final part, calculating the estimated chance to get an australium:

 

AusC = AusT / KFP

    ~= 0.027698554169142405 (2.7%)

 

Not bad. Screw unboxing 3rd gens, this is the way forward, plus it's fun. For the actual chance though, I suspect one of these three potential values: 2, 2.5, 3

 

2.5 seems the most likely, that's a pretty human number, right? So have we solved the mystery? Maybe. Hopefully.

 

Bonus

 

So, about the Frying Pans... Pretty simple calculation as well. We keep the pan's -80 KF in the KFP, so don't get confused about that.

 

PanT = 40

PanC = PanT / KFT

    ~= 0.0003961180431768667 (0.03%)

 

I think 0.05% is the most likely actual drop value. Or 0.01%, who knows. Either way, the chance is really small but it's there :)

 

Happy MvMing!

 

tl;dr


AusC ~= 0.027698554169142405 (2.7%)

2.5% or 3% probably

 

PanC ~= 0.0003961180431768667 (0.03%)

0.05% or 0.01% probably


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cares Newbie

cares

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your chance of getting an australium is 100% providing you have 20 keys .... (roughly)

 

No. There is always you don't get an australium ever, up to infinity. That's the nature of random chance.

 

Very very likely is not 100%.

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knavesmith Newbie

knavesmith

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your chance of getting an australium is 100% providing you have 20 keys .... (roughly)

Percentages are not accumulative, they are multiplicative.

 

The chance of getting heads from a coin flip is 50%. The chance of getting 2 heads from 2 coin flips is 25%, not 100%.

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FireStarter101 Newbie

FireStarter101

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Just want to let you know that I did the math on the australium drop rate a while back.  I recently updated it, and it is in the tf2 economy section.
 

 

TF2 Economy page

http://forums.backpack.tf/index.php?/topic/7939-the-real-australium-drop-rate-047/page-3

 

Australium Weapon Drop Rate 2.0

https://docs.google.com/spreadsheets/d/1dJWmNnptCy3BZClNi4JQHDPloRZPt4nXhGj-wJu6CBg/pubhtml

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FireStarter101 Newbie

FireStarter101

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I felt that badge level was the most accurate way to account for tours done. the only way to skew the information would be to delete your badge.  understand that there have been some that has deleted their badge. but I believe they are the minority. 

 

as for the fabricators  and killstreak kits  there are too many variables to account for. first the quantities on stats.tf  fluctuate up and down. if you check the quantity of australiums  day to day keep an eye on how many per level you will notice the quantities change up and down. ( i use australiums  as an example because of their rarity. there are more fabricators earn each day then are made into kits to notice a drop in quantity.) you also have to take into consideration the extra kits given in the left hand column. in my past 25 tours I have received 12 extra kits. if it wasn't for valve releasing crate 83 and 84 you could determine how many tours were done by adding all killstreak kits and every killstreak weapon in the game. that would almost be impossible to do.

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cares Newbie

cares

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-snip-

 

As mentioned, stats.tf does not forget items. There is no definitive way of knowing if a kit or fabricator has been used, or traded away. Killstreak weapons do not have a tag linking to the used kit or fabricator's original id. According to your calculations stats.tf is missing 1.2 million fabricators/kits in the index at the very least. Either that's a bug with stats.tf or you're wrong.

 

And although yes you can get fabricators in the left hand, the large data sample makes it less significant and rounding solves the issue.

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FireStarter101 Newbie

FireStarter101

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last night there was 181 Blutsaugers in backpacks when i did my spreadsheet now there are 178. stats.tf can only count what it can see.

 

http://backpack.tf/stats/Strange/Australium%20Blutsauger/Tradable/Craftable

 

                                    was         Now

Force-A-Nature            170        169

 Frontier Justice           167        157

Grenade Launcher       130        120

Medi Gun                     113         107

 Scattergun                  148         141

 SMG                           151         144 

Stickybomb                  129        122

Tomislav                      178        167

Wrench                        129        126

Eyelander                      37          34

 

Keep an eye on it for a few days you will see it go up and down

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