# Tagged Questions

The randomness tag has no wiki summary.

0answers
34 views

### 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 ...
0answers
31 views

### Is my One Tail Hypothesis correct?

Testing the sale of marijuana in Colorado and Washington before and after legalization. The numbers are made up and random. ...
0answers
42 views

### Determining sample size in a non-normaly distributed data

I want to take some samples from a database nearly ~150.000 records of a non-normally distributed values. From this link I obtained some common procedures to find a sample, influenced by The level of ...
2answers
60 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 ...
1answer
43 views

### 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 ...
1answer
50 views

### randomness and computers

How do computers achieve randomness if they really do ? How to decide whether something is random or not? Is there a measure of randomness? ...
1answer
75 views

### 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 ...
0answers
38 views

### 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 ...
0answers
48 views

### ascertaining the randomness of a list of numbers [closed]

Assume that I have a series of DNA mutations occurring at specific positions x= [2, 3, 10, 14, 20] drawn from a sequence of length 50.( has positions 1 to 50) How ...
2answers
109 views

### 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 ...
1answer
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### Why is the ROC curve of a random classifier the line $x=y$?

The title is my whole question.
2answers
447 views

### 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 ...
0answers
58 views

### 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.
2answers
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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 ...
0answers
56 views

### Stock price max / min strangeness

Stock markets are often described as following a random-walk or something similar. I have a process that automatically picks a trade entry time and a trade exit time for a given stock. After 1000 ...
0answers
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### Estimating the randomness of an SRS

I have noticed that normal population parameters can be estimated accurately with a reasonably small sample. It occurs to me that this is only possible because of the assumption that the random ...
1answer
54 views

### 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 ...
1answer
116 views

### 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 ...
0answers
174 views

### 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 ...
0answers
93 views

### measuring randomness using runs test [closed]

I try to measure the randomness of data using the runs test (beside the chi square test). I get following values for a file produced by /dev/urandom: ...
2answers
149 views

### 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 ...
3answers
157 views

### 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 ...
2answers
174 views

### 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 ...
3answers
388 views

### 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 ...
1answer
688 views

### 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 ...
2answers
124 views

### 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 ...
1answer
120 views

### 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 ...
1answer
98 views

### 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 ...
2answers
260 views

### 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 ...
6answers
746 views

### 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 ...
0answers
61 views

### 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 ...
1answer
210 views

### Is there self-similarity in true randomness? [closed]

Would a truly random function exhibit self-similarity? By truly random I basically mean that if you have some function that produces a binary value, each new value will have exactly 50% chance of ...
3answers
2k views

### 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 ...
2answers
323 views

### 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 ...
3answers
303 views

### 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 ...
1answer
58 views

### 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. ...
1answer
509 views

### 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 ...
2answers
145 views

### 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: ...
4answers
617 views

### 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, ...
0answers
419 views

### 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 ...
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