The chances of him being Rng are astronomical.
The proof: Voidfang vestments
There are 6 types of armor exotics for the Warlock: 1/6 chance of getting the voidfangs, or roughly 16.66%
Now to get the probability of this happening 4 times in a row, we simply take 0.1666 (16.66% in its decimal form) and put it to the power of 4.
So what does 0.1666 * 0.1666 * 0.1666 * 0.1666 get us: 0.0007703
Now converting 0.0007703 to a percent we get: 0.07703% chance (roughly) of getting the voidfang 4 WEEKS IN A ROW.
I'M SPEAKING OF THE MATH OF GETTING IT FOUR WEEKS IN A ROW NOT ON A WEEK BY WEEK BASIS.
We can from this data assume that Xur is not RNG.
Conclusion: Bungie enjoys taking baths in the salty tears of Warlocks.
Edit: Well a few people seem to have a problem with my math, so if you do, would you mind posting something correct. Aswell as I did not take into account that some items may be weighted more then others.
Edit 2: In response to everyone saying that I was to quick to jump the gun that Xur is not RNG, well you are right, there is still a chance that it may of in fact happened, but i stand by the fact that there is a 0.07703% chance of this happening, so i assumed that this would not of happened.
Edit 3: Number 1: Yay look at us being all fancy and trending
Edit 4: Trying to maybe sleep but so many buzzing phone notifications
Edit 5: someone brought up the point that one of the multiple factors may be to decide between arms, chest, and helm, then decide between exotics which does make some sense for the sun-breakers incident.
but this brings the chances down even lower: around 0.01928125% chance
Edit 6: If anyone from bungie reads this would you be able to confirm or deny the randomness of Xur?
Edit 7: back from school
Edit 8: It has come to my attention that some people may be misunderstanding my work, I'm not saying the probability of him getting the voidfang this week is 0.077% I'm saying the probability that he were to sell Voidfang 4 weeks in a row is 0.077% (Assuming he sells all exotic armor, and that all are weighted evenly, which i either believe some are weighted more, or its pre-chosen!)
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Edited by CaptainChortles: 11/28/2014 11:35:08 AMYour post follows the same logic as this. [quote]There is a raffle with one grand prize and 1,000,000 participants. Bob got the prize. The odds of Bob being the one to get the prize are 1 / 1,000,000 = 0.0001%. Thus, we can tell that the raffle was rigged in Bob's favor.[/quote] Hopefully, you can see how illogical this is. He sells three items a week, all of which have six possible options. Assuming equal weighting, the odds that one or more of these items is the same as the week before any time he comes is ~42%. (5/6 chance for each slot it'll be different, odds they are all different is (5/6)^3, odds one or more are the same is the inverse of that) Knowing you, if he sold The Armamentarium twice you'd be posting about how that's only 2.78% odds. Yes, technically the odds of rolling that [i]specific[/i] item in that [i]specific[/i] slot twice is 2.78% in [i]exactly two rolls.[/i] You'd look like a blundering idiot, however, as the real thing that matters, the odds of [i]any[/i] one of his three armor pieces being the same as last time, is 42%. Under 3%, 42%. Seeing the difference? It's the same as the fact that there was a 0.0001% chance that Bob would win the raffle, which means [i]nothing[/i] because there was a 100% chance SOMEONE would win it and whoever won it, it would be unlikely. Moving on. In three weeks, the odds of getting the same armor, any piece of armor, in a row 3 times is a little above 7%. 4 times is a little above 1%. However that's not exact (I treated the odds for "one or more" being a duplicate as "one" being a duplicate, which will give slightly lower odds than the real thing, because I'm lazy.) and only holds true if he only showed up 4 times. He's appeared a dozen times. So then we have to get into the odds of what's the likelihood of any of the three slots rolling any item four times in a row within twelve rolls if you want anything meaningful. Even that is assuming that everything is equally weighted. Also, please people, in the future, do not use this logic. You can do this with anything. You can see a license plate containing something meaningful to you and calculate the exact odds of that exact car having that exact plate, blow your mind and believe that aliens are manipulating the traffic. That, or you can realize that you pass an astounding amount of cars on the road every day and each one of them has a chance of having a plate that means SOMETHING important to you. The odds of getting a specific abnormal pattern is small but the odds of getting [i]any[/i] abnormal pattern is pretty big. The odds of getting Voidfang Vestments 4 times in a row in 4 visits is extremely tiny but the odds of getting any of the 18 armor pieces Xur sells over 3 slots 3-4 times in a row in 12 visits is not all that small. --- Note that this is not a comment on whether or not Xur is controlled by RNG. Just that the fact he sometimes sells an item 3-4 times in a row is not solid proof that Bungie is messing with us.