Math- Can't Truss' It

You know an article is going to be awesome when the title contains a Public Enemy quote.  Those of you that have been following my work on Dick Move already know that I'm a sucker for math.  I enjoy a good round of mathhammer nearly as much as a game of Warhammer.   Statistics and probability are things that you really need to have a grasp on to elevate your game.  Knowing the odds of killing an enemy, surviving a reckless action, or passing a leadership test are invaluable in my own decision making process.  I won't lie and say that I always calculate the exact odds of accomplishing what I want, but I know that if I want to take down a Landraider with missile launchers, it's going to take more than just a handful of shots to do it. 

Don't fret if you're not math savvy.  Heresy Online has a good 40k combat calculator that can help you out of a jam. 

Having said that, I will also let you know that I am extremely mistrustful of the application of probability to a game of Warhammer.  Frankly, you are rarely going to be rolling enough dice at one time for the outcome to logically follow predicted outcomes.  Perhaps something like Khorne Berzerkers on the charge come close, but keep in mind that rolling 20 is less likely to behave as we would assume, but rolling 1,000 dice would probably yield pretty close to average results.  Rolling an infinite number of dice will yield average results. 

Here is a real life example based on a series of highly improbable events that happened to me recently.  It's centered around these assholes here:

Yeah, these assholes
This past weekend I got a chance to play my first game of Warhammer Fantasy 8th ed against my good buddy Hoagy.  He already went to the trouble of making up a battle report, so if you're interested in reading it or seeing more pretty pictures of mostly unpainted miniatures on my desert board you can read it here.  For me, the game was fraught with bad luck from the outset.  Turn 1 saw my cannon misfiring itself to death after my Lvl 4 Life Wizard miscast and killed 3 greatswords while resurrecting 3 crossbowmen- not a good trade off to say the least.  Over the course of the next few turns I lost both my other artillery pieces (a mortar and a Helstorm Rocket Battery) to misfires- it was a small game and I was more interested in trying out as many things as possible than having a cohesive army, so I didn't have a lot of artillery and didn't get to spam anything. 

Anyway, let's crunch the numbers on my suicide artillery.  I took a total of 5 shots over the course of the game.  3 of those were fatal misfires. 
  • 1 result on the artillery die is a misfire, so the probability of rolling a misfire is 1/6
  • 1 result on the misfire chart (a roll of 1) results in a wrecked piece, so the probability of being wrecked is 1/6
Noting the above, the probability of an artillery piece getting killing itself with a misfire on a single shot is 1/6 * 1/6 = 1/36

This also means that the probability of not killing itself (inclusive of non-destructive misfires) is 1 - 1/36 = 35/36. 

Since in my particular case I got 2 shots off and died on 3 others the odds of that happening were:
(1/36)^3 * (35/36)^2=  1,225/60,466,176 = .00002026... or odds so low that my calculator just had to resort to scientific notation.

I stood a 0.00203% chance of exploding my 3 war engines over the course of 5 shots.  Ordinarily when you fire a cannon or what have you, you assume that you're going to the shot off.  Statistics even tell you that you have a 35/36 (97.2%) chance of at least not destroying yourself.  Seems like a pretty safe gamble.  Hell, I'd take odds like that in Vegas all day long.  Sadly, just because something is likely to happen doesn't mean that it is guaranteed to happen.  Despite the fact that there was nearly 100% certainty that I would not lose all of my own units to misfires, it happened.  Shit happens. 

And that my friends is the moral of the story.  Shit happens.  Despite your best efforts and confidence in  statistics, you can't expect all of your rolls to behave as predicted.  Even if you know that firing 10 lasgun shots at BS3 will yield 5 hits on average, it is still possible or even likely that you will get 4, 6, 10, etc hits when you roll.  At the same time, even though I know that shooting a single missile at a Landraider at BS4 only stands a 11.11% chance of glancing, so it's not worth the effort if there are other viable targets.  If anything is to be learned by this, it's that knowing your stats will help you to make logical decisions, but don't be surprised when things don't work out quite as you expected.

So there you have it.  Anybody else pulled off any ludicrous rolls?  Got advice for applying stats to your game?  Inevitable math errors to bitch about in my calculations?  Sound off in the comments section.

11 comments:

Thor said...

This comment has been removed by the author.

Thor said...

Fucking Blogger decided to eat my last comment. Round #2:

Very true. Mathhammer is a useful tool but never one to completely rely on. What it does do is give you an idea of how likely something is, or is not, to happen and you can make an informed decision. Nothing is absolute in a game of chance.

Alex said...

One of the infamous stories from my old gaming group was where I bluntly stuck a Falcon in the face of four devastator marines on top of building and fired with the scatter laser (back with old codex where you rolled for the number of shots) hitting and wounding four times. Right before rolling for armor, one of my friends watching the game turns to my opponent and says something to the effect of "just don't roll four ones" and BOOM - all four armor saves come up ones. Cursing and laughter ensue. Thus the legend of "four-ones" was born.

Chumbalaya said...

I took my Loganwing up against a DE army full of paper planes. A boat load of S8 shots going first against open-topped AV10 should be no problem, right?

Ha ha, everything I rolled was a 1 or 2. Not much you can do but have fun with it.

GMort. said...

I once had to roll 6 dice for saves on my Assault Terminators and rolled 5 1's out of the 6 dice.

I don't even want to work out the mathematical likelihood of that happening again...

Pschutte said...

I had a Thunderwolf Lord with frost axe charge a squad of guardsmen I had all seven hit and then rolled seven ones to wound. My Lord then took a wound failed leadership and fell back 15 inches.

Nikephoros said...

I was a history major not math, but doesn't 1/6 * 1/6 = 1/36? That would make your luck even worse.

Dethtron said...

nikephoros: right you are. that'll learn me to try and do remedial math in a hurry while half asleep :)

I fixed the errors in question above, but it really only impacted the final result by 2*10^-6 due to the already ludicrous improbability of the situation

DFM said...

@Gmort Thats why you will never hear me say "They're only guardians" or "only flashlights" ever again.

5 guardians, 5 dead deathwing. After the split second "wtf?!" moment, I got over it.

Ian said...

Obviously you will not always get average results, but mathhammer still provides you with the ability to say "this is what will probably happen" rather than "I have no idea what's going on" or resorting to anecdotal evidence that's always skewed by confirmation bias.

MadPersian said...

I love how odds end up working on the small scale of a wargame. I really like that it truly is pretty damn random. I do the whole mathhammer thing so I can make an informed decision (as the author and many of you have said), but when I roll the dice I have no expectation for the dice to follow the odds.

That's why I don't get upset at bad rolls or behave superstitiously when rolling dice.