Questions relating to (pseudo)randomness, random oracles, and stochastic processes.
Questions tagged [random]
1860 questions
2
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A set of conditions to prove or disprove randomness
I am trying to understand the heuristic connection between fitting a normal distribution to a dataset and the definition of what constitutes a random process.
If a normal distribution fits your data much better than other competing fits, then I…
warship
- 162
2
votes
1 answer
Fast method to pick unique random numbers?
In general, computer simulation involving random numbers (lets say to simulate a fair deck of playing cards so $1$ thru $52$) runs fast if you only pick a few cards. However, as you pick more and more, the algorithm slows because of "collisions",…
David
- 1,702
2
votes
2 answers
Need Randomness within constraints
The wife wants to make a quilt from squares of fabric cut from my old shirt. Awesome.
Situation:
2” x 4.5” blocks of fabric containing various patterns.
Quilt should be 17 across (4.5” the long way) and 36 down.
612 total blocks will be…
Mike Larsen
- 21
2
votes
1 answer
Can a collection of random processes be not random?
A friend and I were having a debate about randomness and at one point, I said that it was possible to have a collection of random processes which were not random when "put together." He disagreed.
So, I put the question here more concretely and…
Jeel Shah
- 9,306
1
vote
1 answer
Random conversions
I came across a question in StackOverflow which states the following, all is based on natural numbers:
Given the function rand5 (which produces random natural numbers 0-4), use it to generate a rand7 (which produces random natural numbers 0-7).
I…
Martin
- 111
1
vote
1 answer
Generate random results in a continuous field
How can we generate random results for a field like economical predictions where there is no limited number of results (contrary to a coin with 2 results) and also contrary to a random walk with steps with a fixed length (in either direction).
Quora Feans
- 1,059
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vote
2 answers
Exercise on Random Variables
I´m struggling with a random variable exercise of a book I´m reading. Anyone has an idea of how to approach this problem?
Thanks in advance :)
Pablo Estrada
- 275
1
vote
1 answer
How to place random points on an egg?
While I was having breakfast this morning, I thought: "I know how to put random points on a sphere or a torus, but how to place random points on an egg (with uniform probability with respect to any area of the egg)?"
Assume this equation (proposed…
VividD
- 15,966
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1 answer
Can 3 random variables have pairwise correlation -1?
Can 3 random variables X, Y, Z have pairwise correlation -1?
This seems to be easy question, but I just got confused over this.
Confusian
- 93
1
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2 answers
Questions about averaging
i have some trouble with averages. Here are two questions rolled in one:
why is :
$$\frac{\prod _{n=1}^N \left(1-\text{rnd}_n\right)}{N} \neq \prod _{n=1}^N \frac{1-\text{rnd}_n}{N} \mbox{where $rnd_n$ is a random gaussian real} $$
And how can i get…
tarrasch
- 117
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vote
0 answers
Determinate State of Linear Congruential Generator from Results
I am curious on how someone would go about determining the state of a Linear Congruential Generator given its output.
X(n-1) = (aX(n) + c) mod p
Since the values returned are deterministic and the formula is well known, it should be possible to…
Martin
- 11
1
vote
1 answer
Generating Auto-Correlated Random Numbers with finite correlation length
How can I generate a lot of (for example N=20000 or more) auto-correlated random numbers {x_n, n=1,2,...,N} with uniform or normal probability distribution and finite correlation length (Here eq. correlation length = 3), i.e.…
Mojtaba Golshani
- 408
1
vote
1 answer
create random random whose sum is constant
Given N numbers. How can I decompose each element x in N into random values r1,r2,..rk (k can be a variable) such that the their sum is equal to x. What can we do if the rs are integers or irrationals or real numbers (maybe from zero to one)?
Note…
SaSa
- 51
1
vote
1 answer
How to perform a random split on a value
I have 30 dollars, randomly split it into 3 parts, and send it to persons A, B, and C.
After playing an infinite number of games, the expected payoff of each person can be:
Case A
person A: 15 person B: 7.5 person C: 7.5
Or
Case B
person A: 10…
tung
- 11
1
vote
1 answer
Sequence of independent $X_n$ with $E(X_n)=0$ but sample mean diverging to minus infinity
I am asked to construct a sequence of independent random variables $X_n$ with $E(X_n)=0$ for any $n$, but the sample mean of the $X_n$’s diverges almost surely to minus infinity.
I understand that the only condition not mentioned here to fall into…
JenniferK
- 19