The tag has no usage guidance.

learn more… | top users | synonyms

0
votes
0answers
15 views

Testing covariate balance (for RCTs)

I have a block-randomized data-set of households. I.e. whole villages are assigned to treatment or control. (On top of that I have a regional stratification, i.e. in each region the same number of ...
4
votes
3answers
84 views

Nonrandomized better performance

On the footnote of page 497 in Jaynes' "Probability Theory: The Logic of Science" he writes Of course, Fisher’s randomized planting methods – which we think to be not actually wrong, but ...
0
votes
0answers
16 views

Biased coin randomization with adjustments over time

Assume an experiment that was going to consider different randomization strategies to address different challenges. The experiment involves an experimental (active treatment) and control group (usual ...
1
vote
0answers
13 views

Would using the md5 for treatment assignment introduce any biases?

Disclaimer: I'm not sure if there's a better stackexchange for this, but since I consider experimental design an integral part of causal/statistical inference, I'm hoping this is an appropriate ...
0
votes
0answers
18 views

Bootstrap versus randomization test

I am re-analyzing a natural experiment. The outcome is the # of events of a particular type. The units vary in geographical size. There are two conditions. In the original analysis, the authors took ...
1
vote
0answers
30 views

About the Randomized Dependence Coefficient

In the paper The Randomized Dependence Coefficient, authors introduce a novel dependence coefficient which seem to be quite generic and powerful compared to what is present in the literature. It is ...
0
votes
0answers
5 views

IN PLSA how can we ensure that with k topics we won't get some duplicate distributions

I mean, if we initialize our topic coverage coefficients for document pi_d and word probabilities for each topic P_w with random ...
3
votes
1answer
48 views

Is re-randomization valid approach to estimate statistical significance

I am a newbie in statistics and I'm taking Khan Academy course. There is one video I don't quite understand. Here's the gist. A statistican wants to know which bus gets her to work faster: A or B. ...
1
vote
1answer
53 views

Two sample tests for stratified randomization

I have to test the difference between two samples which were selected via stratified randomization. The problem is that the samples are not independent due to randomization was stratified. How should ...
0
votes
0answers
14 views

Model variables don't match stratification variables

Okay, so here's a puzzle that I recently encountered. Suppose I am interested in modeling a treatment effect (measured as a continuous variable) on a population, stratifying on a dichotomous ...
5
votes
1answer
213 views

Is tossing a coin a fair way of randomising a group into two groups?

So myself and my uncle are having an argument over whether a coin flip is truly random. I argue it isn't because in real terms a coin tosser will always manipulate a coin so the result isnt 50/50 ...
2
votes
1answer
40 views

Test to compare distributions using the intersection area of the densities

I have to compare several distributions, but I don't want to use Kolmogorov-Smirnov test, since I'm dealing with big data ($N > 10^{6}$) and traditional hypothesis tests end up with detecting the ...
1
vote
1answer
53 views

Can a truly randomized procedure (e.g. random treatment allocation) result in unbalanced distributions?

Thousands of randomized trials are ongoing or in the planning. These trials rely on randomization procedures (e.g. patients being randomized to either placebo or active drugs) to yield two balanced ...
0
votes
0answers
26 views

Can you exclude one country as robustness check in multilevel cross-country model?

I am conducting a multilevel study in which individuals are nested in countries. As a common robustness check in normal linear regressions, we can exclude one or a few countries with special ...
0
votes
0answers
19 views

Random Sampling Techniques

I have a pool of people who each have at least one email associated to him/her. Two people can also share a single email. This results in clusters of people chained together by email:person units. ...
1
vote
0answers
32 views

Why would one not stratify random assignments in a controlled trial?

With some frequency I read reports of randomized controlled trials where, despite the randomization, a baseline survey found significant between-group differences in important covariates. It seems to ...
2
votes
1answer
611 views

Sample size and power calculations for a randomized controlled trial

I need help with the power calculations to determine the sample size of a randomized clinical trial. This is a relatively simple trial with two arms: an intervention arm and a control arm. Patients in ...
0
votes
0answers
29 views

If 4 Peaks is GA-friendly, why is it getting stuck in a local optimum?

First, 4 Peaks: Given numbers N and T, an instance of 4 peaks,x, is an N-length bit string. We rate its fitness by doing o(x) = Number of leading 1s, z(x) = number of trailing 0s. An extra REWARD=N is ...
2
votes
1answer
220 views

Advantages of counterbalancing vs. randomizing stimuli

I'm designing an experiment, in which 40 participants answer 10 questions, 5 in condition $A$ and 5 in condition $B$, and I'm interested in the difference between the two conditions. It's not clear ...
3
votes
1answer
124 views

Is this a Random or Purposive Sample? Inclusion-Exclusion Criteria and the Sampling Frame

Introduction I am confused about when a sample is a random sample (i.e. probability sample) and when it is a purposive sample (i.e. non-probability sample). My understanding is that the former allows ...
2
votes
0answers
30 views

What is re-randomization?

I'm a statistics newbie, taking an online course, and the term "re-randomization" was thrown in without explanation. What does it mean?
0
votes
0answers
37 views

Randomization for multi-site clinical trial, screen failures

Two questions about appropriate randomization procedures for a small two-armed trial at 3 sites. About 100 participants total, evenly split between study arms. First, we are concurrently enrolling ...
0
votes
0answers
52 views

Comparing the Magnitude of the Difference in Variances Between Groups to Identify Selection Bias

I'm comparing two populations--private and public sector accounting firms in the state of Rhode Island--for differences in the distribution of quality/ability of the accountants who work at those ...
3
votes
3answers
49 views

how to include distance buffers in cluster randomized trial

I need to incorporate distance buffers into the selection of treatment and control units in a randomized-controlled trial in order to minimize spillovers between arms. Cluster in this study is a ...
1
vote
1answer
72 views

Can confidence interval from hypothesis test inversion ever contain observed difference if that difference is significant?

My question concerns the method for constructing a confidence interval for a difference in means based on a randomization test (that can be found here , check under 'Confidence interval based on the ...
0
votes
0answers
27 views

Principles for choosing randomization procedure - example from tournament data

I have read many very useful posts on this site as regards randomization procedures. I wonder if the following example may be useful for discussion purposes. My basic question is which of two ...
0
votes
1answer
73 views

Randomization software/service for clinical trial

I need a software/web-based system for the clinical randomization. This software/service should have the capabilities for handling stratification, multiple centers and block. The sample size of ...
1
vote
1answer
35 views

Is it possible for two independent people to generate randomness?

It is well documented that people are not very good at generating random sequences. However, is it possible that two people, working independently, could generate randomness together? Consider the ...
1
vote
0answers
146 views

How is the constant in Marsaglia's xorshift* RNG determined?

I get Marsaglia's basic xorshift RNG. For further randomness he suggests multiplying the result by a "suitable constant." This is some code I've found that does just that: ...
0
votes
0answers
30 views

Generating a dataset from mean, standard deviation, n and 95% CI

I have the output of a couple of Socprog models and I'd like to see if the results are statistically significant. Group A output: ...
4
votes
0answers
68 views

What kinds of PRNG exist outside Linear congruential generators?

I'm kinda running out of words, Linear congruential generator are really low quality PRNG but it was all I needed for some basic stuff, now I need to fill the blank and get to know other families of ...
1
vote
0answers
18 views

Correcting for multiple comparisons using simulated distribution

To check if unilateral pairs (defined below*) are coordinated (i.e. move together) in a flock of N coordinated individuals, we generate hypothetical (null) distribution of a certain focal parameter of ...
6
votes
2answers
371 views

Test the randomness (uniformly distributed) on a 64 bit float random generator

We have a random number generator which is supposed to generate 64 bit floats, uniformly. We want to test whether it is a good uniformly random. I am not asking the general way to test it, as it was ...
2
votes
0answers
73 views

Randomization test and comparisons of many to 1

I have about 80 different groups, each with 3 replicates which I would like to compare against a control having always a value of 1. As I have a low number of replicates and many groups having 2 ...
1
vote
0answers
28 views

Randomization Testing help

I am scratching my head over this one...any help would be greatly appreciated. I want to know if the average travel time between Guell Park and the beach in Barcelona using the bus or the metro ...
4
votes
1answer
34 views

Randomisation for 2 site clinical study

If I want to conduct a randomised study in 2 sites comparing two clinical treatment arms, and every site is expected to include 60-80 patients, is it acceptable to randomise every new patient with ...
8
votes
2answers
345 views

Using control variables in experiments?

Why would one want to control for any number of baseline covariates in a situation where the assignment to treatment group is random? My understanding is that randomly assigning treatment should make ...
5
votes
1answer
430 views

How to calculate permutations of categorical variables with R

I want to simulate or calculate probabilities of combinations of group membership for different sample sizes (e.g., n= 3, 4, 5, 10, or 100) for two groups (of the same sample size). Each outcome could ...
2
votes
2answers
139 views

Does randomization really allow us to make claims of causality?

Lets say two groups are compared. Subjects are randomly assigned to each group, then a treatment is given to half while a placebo is given to the other half. All aspects of the experiment (order of ...
4
votes
3answers
187 views

Question re permutation tests for a relatively complex data set

I regret that I cannot be overly explicit due to confidentiality agreements. I will try to state my problem by analogy. Suppose that you have two groups of people, one with a condition and one ...
0
votes
1answer
322 views

MULTIPLE TESTING: Probability of specific outcomes from MULTIPLE experiments using randomized data

This is a follow-up question to this one: Significance test across multiple simulated experiments There's one answer I'm leaning towards accepting, but I wanted to make sure I understood how ...
0
votes
1answer
55 views

Calculating the probability of 31 of 628 items are sampled (no replacement) more than 10x amongst 150 participants drawing 50 items each

I am sorry for having to ask a simple probability question, but I have been thinking about it for weeks and an extensive google search has given no answers. I have a group of 628 questions. 31 ...
10
votes
2answers
509 views

Is randomization reliable with small samples?

Jerome Cornfield has written: One of the finest fruits of the Fisherian revolution was the idea of randomization, and statisticians who agree on few other things have at least agreed on this. ...
8
votes
3answers
519 views

What examples of lurking variables in controlled experiments are there in publications?

In this paper: Lurking Variables: Some Examples Brian L. Joiner The American Statistician Vol. 35, No. 4, Nov., 1981 227-233 Brian Joiner claims that "randomization is not a panacea". This is ...
2
votes
1answer
183 views

How to get proper randomization in website A/B testing?

In the statistical practice of experimental design, you separate your tests by 'blocks' if you can control the factors (say routing to one page or another, or categorizing by browser) or through ...
2
votes
0answers
108 views

$p$ value for a randomized test

For a randomized test, how do we compute the $p$-value? For example, suppose the test is of the form: $\phi(X)=1$ if $X > c$, $\phi(X)=p$ when $X=c$ and $\phi(X)=0$ otherwise. How do we compute the ...
2
votes
0answers
33 views

Confidence interval(s) for randomization design

I am developing a method to do something with permutation testing. I have two permutation / randomization schemes and do not know which one is better than the other. Can I find the confidence interval ...
1
vote
0answers
71 views

Statistical significance problem

I've got an algorithm which assigns a score to a list of individuals (nodes). I want to discover which nodes received a statistically significant score. So I "randomized" the algorithm in order to ...
-1
votes
1answer
113 views

How do I randomize a larger population, from an existing population in R?

I have a small 20k (176 variables) test dataset. I want to create a random bigger dataset for testing, using the rows (data) and columns (names) from the small dataset. Currently I have: ...
1
vote
1answer
47 views

How to test whether variables are more frequently associated than expected by chance?

I have this presence/absence matrix (S2 is missing on purpose). ...