Btw even precisely 5 times in a row would be hard and I don’t think you answered that.
Hm, I didn’t consider the amount of consecutive runs was relevant. It’s not like chance to drop in each session changes, is it? Obviously, if I am to do “infinite” amount of runs I can get 1 billion of the same item to drop in a row - just like with monkeys and typewriters, basically.
Anyhow, I remember starting the game session and getting them blue pistols 5 times in a row from the first run.
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It’s kinda philosophical or rather we’re trying to ask a question that’s most useful.
The simplest probability would be what was your chance that day to get it in the first 5 runs.
But maybe if you played in other days you could get it then and also remember it and talk about it in this thread 
What I’m saying you could have been playing 7 sessions 5 runs each day and you’d remember the session it happened
Yeah, but… well, you’ll have to forgive me since I’m bad at math and probabilities (my knowledge on that decayed fast because I don’t use it much), how the amount of runs before getting 5 in a row is relevant? I could’ve done maybe 1000 runs before and not getting a single one, but from runs 1001 to 1005 I would get it each time.
Blue Garg’s pistol, according to GT, has a 7.5% drop chance. So getting two of them in two runs is 0.075^2 = ~0.006 = 0.6%?
Or is it (1 - 0.075) * 0.075?
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The formula is easy.
No drop = sad. No many drops = bad game.
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You yourself said that if you do a large numbers of runs, the probability of getting 5 consecutive get higher.
This is the probability of you getting this gun in two runs.
But I’m asking you - did you only do 2 runs?
Did you say to yourself - today I’ll do these 2 runs and if I drop guns two times, I’ll write about in on the forum.
Or was it as follows. You were farming some stuff for quite some time.
And some point you noticed 5 guns dropped and you remembered it.
That kinda a different story and the probability of you having such a story
is much higher than p ^ 5 because it could happen earlier for example.
Maybe the events we should be considering are actually different, that’s what I’m saying.
Maybe we should count what’s the probability of 5 consecutive guns while you were farming your stuff.
Not what’s the probability of 5 consecuitive guns in particular runs you did on a particular day 
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Hm, yeah, that makes more sense now - at least I think so. The main reason I was confused though was that there’s no way of telling how much runs was before that (I’m playing the game for almost 2 years now, after all XD). So it was like that: I did X runs and got Y guns, but some time throughout those X runs was a moment when I got 5 guns in a row.
I was thinking maybe it was similar to proc chances of celestial powers for example (like in the topic I made ~a month ago and you said about using Phantasmal Blades for x5 projectiles).
Like, for example, if Howl of Mogdrogen is bound to Ring of Steel, it has 68% chance to activate. Lets say we fight a single enemy. We cast RoS one time and have 32% chance to NOT activate it. We cast it the second time and have the same 32% chance, but overall chance of not activating it two times in a row is ~10%. But I guess it’s a different case.
Dude that’s the best stuff I read all day! XD
Now I know why @tqFan popped into my 4-year-old GDLoot thread.
Serious Stan is correct in everything he said. 6.5% drop chance.
The 15% thing brought up by @Gnomish_Inquisition is (I assume) incorrectly labeled as a % but is instead the result of inverting the drop chance.
As far as calculating the number of runs required to expect such a drop, I’m not great at that sort of math (statistics) but it does involve an EV (Expected Value) calculation. I defer to this article from the Warframe wiki for an explanation:
On the other hand, this website gives us this estimate:
69 runs. Nice.
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Nice
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Haha, thanks for clarification 
Indeed this was the reason but I read your script doesn’t work for Chests only for Enemies.
(another thing it not being updated recently).
Hey, actually this calculator is bad.
I mean it’s technically ok but I’d like anyone to think about it.
Why these 90% / 99% probabilities, Expected, Nearly guaranted etc calculations
(look at the math explanation below the calc)
there are not that useful and don’t relate to how we usually play?
What we usually want to calculate when calculating 99% probability?
What is the author calculating and what we would actually want to calculate?
(and that it’s actually much harder which is the reason why it was not chosen)
Hint:
let X be a number of runs needed to drop an item
The 5 guns question, can be replaced with coin flips.
After searching for a bit, I found this document describing it well. It is even using unfair coin, so just plug in the % drop.
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Thanks, actually I was discussing it with @Ulvar1 privately and he also found some recursive formula:
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I have literally no idea what you’re talking about (mostly because that doesn’t read like English).
I mean…doesn’t it? The calculator is telling you that there’s a 99% chance that in any one of 69 (nice) runs, you’ll drop a MBH.
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Sorry, I made a mistake / didn’t notice one simple thing - calculator is good.
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FINALLY FINALLY FINALLY it dropped. I am not sure of the exact number of runs but it’s 70+ for sure cause I had a stack of 68 blood of chtons I used up for keys + some more hearts which I got converted at the smith in Necropolis. Mine is probably just an extreme case.
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How is that not the same thing ? You will never know how many runs you actually will need (duh, RNG), you will only ever know what a reasonable expectation is
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