Questions tagged [randomness]

Randomness is the lack of pattern or predictability in events. Randomness is often modeled with probability distributions, but can also be generated by deterministic processes.

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Wilcoxon signed rank test on anonymous sample

I carried out a test on a group of 100 people. The test contained 10 questions with 5-point Likert scale answers (1 = Strongly Agree, 5 = Strongly Disagree). After the test was conducted, the group ...
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NIST randomness test fails in random generated bits

I am using the NIST randomness test suite which checks whether a bit sequence is random over 15 different tests. I have problems in verifying if this suite works fine. The situation is that if I input,...
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Finding a sample to represent a known population

Entire Population: 30,000 Known properties of population: Age, gender, height, weight, Ideal representative sample size: ??? This is for a mailing list test group selection. Problem constraints: ...
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Best way to test runs

I have the following sample: ...
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How exactly does the R random number generator work? [closed]

When I generate a random number using the following procedure: set.seed(123) rnorm(1) I would like to know what exactly is happening in this case? Is R reading ...
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How to check if a data sequence is really random? [duplicate]

I wonder how can I test if a data sequence is really random? Of course I can randomly cut it into equal pieces, and check if the correlation coefficient between different pieces on average is zero. ...
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How to select model when different models are preferred with different seeds?

I am trying to apply the lasso or ridge regression to my data set for the feature selection, but different random seeds produce different models. What is a good or universal way to obtain the final ...
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Filtering random guessers from daily surveys

Assume we're polling or surveying people about their predictions regarding some future event. This survey is done every day, and the event they are asked to predict is the same every time. For example,...
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Easy-to-apply tests for randomness

I'm interested in testing a sequence of numbers for randomness. I've done some searching and come across die hard and die harder. However these tests seem to require some expertise to apply, or at ...
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Sanity check to determine if 'random' data on disk drive may have been tampered with

I've got some code that does a Dept of Defense secure erase of disks, and would like to know about a good sanity check to run after the fact. Bottom line, the last write phase of a secure erase of a ...
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2answers
761 views

Best process for randomly drawing an odd and an even number

I want to draw a random number from 1 to 100. If this number is even, I want to then draw a random number from the odd numbers between 1 and 100. If the first number is odd, I want to draw a random ...
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Detecting/analyzing non-random permutations of a random sequence

I am looking for theoretical results regarding how easy it is to detect alteration of a random sequence. The permutation I am most interested in is where a subsequence of the random numbers is sorted,...
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randomness and computers [closed]

How do computers achieve randomness if they really do ? How to decide whether something is random or not? Is there a measure of randomness?
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Differential Entropy

Differential entropy of Gaussian R.V. is $\log_2(\sigma \sqrt{2\pi e})$. This is dependent on $\sigma$, which is the standard deviation. If we normalize the random variable so that it has unit ...
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Relation between statistical randomness, uniform distribution and independence

In Monte Carlo simulation, we often consider how well a sequence of generated points are. If I am correct, one aspect is statistical randomness: A numeric sequence is said to be statistically ...
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Randomly picking from $n$ choices roughly $n$ times. What's the resulting frequency distribution called?

Not sure of the best way of phrasing this question, but I'll give it a go. If I were to randomly choose whole numbers between 1 and $n$ a significant number of times relative to $n$ (say, $m$, where $...
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Why is the ROC curve of a random classifier the line $\text{FPR}=\text{TPR}$?

The title is my whole question. FPR is the false positive rate. TPR is the true positive rate.
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Are the digits of $\pi$ statistically random?

Suppose you observe the sequence: 7, 9, 0, 5, 5, 5, 4, 8, 0, 6, 9, 5, 3, 8, 7, 8, 5, 4, 0, 0, 6, 6, 4, 5 , 3, 3, 7, 5, 9, 8, 1, 8, 6, 2, 8, 4, 6, 4, 1, 9, 9, 0, 5, 2, 2, 0, 4, 5, 2, 8 ... What ...
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How can you select one of two individuals at random using a biased coin

Suppose you are given a biased coin for which the probability of getting a head is $p (0<p<1)$.Discuss how you will select one of two individuals at random using the biased coin.
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Co-occurance problem

I have a series of discrete, purportedly random whole numbers like this: v1 v2 v3 v4 v5 v6 42 23 10 07 01 35 05 02 26 25 49 18 35 18 43 29 26 28 36 59 26 15 34 35 I want ...
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Test data for randomness with repetitions

I have an experiment where I am trying to determine whether the answering behavior of participants can be explained as random answering. I.e. every participants will have to answer multiple questions ...
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Runs Test and Chi Square Distribution

I want to identify random data by applying some tests to the observed byte stream. I used the chi square test already on a frequency analysis, which works fine. To reduce the false-positive rate I ...
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interpreting chi square value for validating random numbers

I am trying to use the chi-square test for identifying random data. I have 256 categories, i.e. 255 degrees of freedom and count the occurrence of byte-values (0-255). As suggested by Knuth, the ...
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When does a random test fail?

I must implement some Chi Square Test to test the randomness of "my" implementation, but I can't understand what this tests really say. The tests are different but what I always do is: divide in ...
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Test randomness of a generated password?

As you know, there are many password generators out there to increase computer security. Suppose I am given such a password (say, a string of letters, numbers, symbols, etc.), is there a way for me ...
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Probability of a randomly generated string being already present in a data set [duplicate]

Possible Duplicate: Simple combination/probability question based on string-length and possible-characters Suppose I have a collection of 1,000,000 unique strings where each string is exactly 10 ...
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What is the probability of n people from a list of m people being in a random selection of x people from a list of y people?

If I am selecting 232 people from a pool of 363 people without replacement what is the probability of 2 of a list of 12 specific people being in that selection? This is a random draw for an ultra ...
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Ljung-Box test: Basic Questions

I'm interested into the Portmanteau tests for fitting ARIMA models and ended up to Ljung-Box test and their implementations for R-statistics. I've read already some relative question on the subject ...
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Can one force randomness in a sample?

I recently spoke to a large qualitative analysis company who were working on in-depth analysis of the potential customers of train company. I asked them how they chose the people to include in their ...
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Is there a Bayesian equivalent to a Wald-Wolfowitz runs test?

I have a sequence of observations and I would like to determine if the observations in the sequence are mutually independent. Wald-Wolfowitz is a non-parametric test that can be used to check for ...
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How to sample randomly from a population?

What do you think about the following method to perform a random sampling: Generate as many floats (between 0 and 1) as individuals using a quantum random generator (each value appears only one time)....
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Random walk with momentum

Consider an integer random walk starting at 0 with the following conditions: The first step is plus or minus 1, with equal probability. Every future step is: 60% likely to be in the same direction ...
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Why is it bad to teach students that p-values are the probability that findings are due to chance?

Can someone please offer a nice succinct explanation why it is not a good idea to teach students that a p-value is the prob(their findings are due to [random] chance). My understanding is that a p-...
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Best way to find non-randomness regions in these or similar count data?

Let say I have data in a shape: [0,0,0,0,1,0,0,0,1,1,0,0,0,0,0,0,0,0,1,0,0,2,0,0,0,....] - so mainly zeros.... However I know how long is my 'signal' and how many counts are they. Is it possible ...
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Can non-random samples be analyzed using standard statistical tests?

Many clinical studies are based on non-random samples. However, most standard tests (e.g. t-tests, ANOVA, linear regression, logistic regression) are based on the assumption that samples contain "...
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How to find out if a set of daily measurements are random or not?

There is a set of daily measurements. Time and measured values are both discrete. I want to find out whether measured values depend on the day the measurement was taken, or whether measurements are ...
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Long tailed distributions for generating random numbers with parameters to control tail heaviness

I have to generate random numbers for my algorithm based on probability distributions. I want a distribution which has heavy tails and is unskewed, which can produce numbers far away from location ...
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How can I even out a random distribution while minimising how far each data point is moved?

I have a software application which uses a queue and multiple processors to process those jobs. Jobs get re-run on a daily basis for customers, but we also have new customers signing up regularly. ...
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Scrambling and correlation in low discrepancy sequences (Halton/Sobol)

I am currently working on a project where I generate random values using low discrepancy / quasi-random point sets, such as Halton and Sobol point sets. These are essentially $d$-dimensional vectors ...
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Is it possible to predict the likelihood of an order of random events?

Sorry if this is a n00b question, I'm just trying to wrap my head around the problem. I am trying to refute conventional wisdom here, so any help is greatly appreciated. And now for the question: ...
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What is wrong with this “naive” shuffling algorithm?

This is a follow-up to a Stackoverflow question about shuffling an array randomly. There are established algorithms (such as the Knuth-Fisher-Yates Shuffle) that one should use to shuffle an array, ...
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Testing (and proving) the randomness of numbers [duplicate]

Possible Duplicate: Testing random variate generation algorithms What's a good way to test a series of numbers to see if they're random (or at least psuedo-random)? Is there a good statistical ...

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