The randomization tag has no wiki summary.
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Homogeneity testing of baseline characteristics in medical trials
I have been reading medical journals and they repeatedly show baseline characteristics of samples from a randomised controlled trial, which they have then tested to ensure no differences between the ...
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If I randomly execute tasks working on some subset what can I say about total coverage of the set over some time period?
Say, there are 5 task to be executed with the following probabilities:
Task-A: 0.6
Task-B: 0.2
Task-C: 0.12
Task-D: 0.05
Task-E: 0.03
Each task works on some subset $k_i; i = 1..5$ (for each task ...
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0answers
57 views
Analysis of randomized experiments
I have data from an experiment in which participants were randomly assigned to one of two groups and asked a series of opinion questions. One group, the control, was not presented with any additional ...
3
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3answers
141 views
Difference between Randomization test and Permutation test
In the literature the terms Randomization and Permutation are used interchangeably. With many authors stating "Permutation (aka randomization) tests", or vice versa.
At best I believe the difference ...
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1answer
45 views
How to perform randomization test for categorical data and/or chi-square?
I am very newbie in statistics and I my problem is as follows:
I have a total set of 20,000 categorical observations (this is my whole dataset, say DATA1) which has a certain proportion of "yes" and ...
1
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1answer
52 views
Randomization Tests
The following data are mandible lengths (mm) of 10 male and 10 female golden jackals Canis aureus in the collection at the British Natural History Museum. The two samples are independent.
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3answers
617 views
What's wrong with (some) pseudo-randomization
I came across a study in which patients, who were all over 50, were pseudo-randomized by birth year. If birth year were an even number, usual care, if an odd number, intervention.
It's easier to ...
2
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1answer
29 views
How does randomization testing for correlating two variables work?
I was going through OpenIntro Statistics[http://www.openintro.org/stat/textbook.php] and came across two case studies in the first chapter
Discrimination against women during promotion - Page 42
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35 views
In a random selection of addresses, determine if users are unable to access one of the addresses
Our client software randomly selects a server to connect to. There are four separate addresses the software randomly chooses from. Two addresses are "old" and two are "new". As many firms need to ...
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70 views
Orthogonal array Design of experiment (DOE) in R (Restricted randomization)
I am designing an experiment using Orthogonal array. I have managed to do it in R as well. However, I missed one functionality that is restricting the randomization. That means, I want to randomize my ...
0
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1answer
63 views
Tests for quality of permutation (Y-randomization)
Can you please suggest the metrics/tests for accessing the quality of Y-randomization (permutation)?
I have some doubts in quality of Y-randomization that I am using with sample.int from R. For 100 ...
2
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1answer
159 views
Stratified randomization with permuted-block randomization
I need to create a computer program for randomizing subjects using stratified randomization with permuted-block randomization, so I want to make sure my thinking is correct:
Suppose that in an ...
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0answers
17 views
how to bound the probability of two data-points being assigned to the same cluster in k-means
Given that I have multiple running of k-means and the same data (say $K_1$ to $K_p$), each one with random initiation. Given two points $x$ and $y$, and their distance $d=||x-y||$.
How can I bound ...
2
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0answers
31 views
Randomised trials: Risk of unknown confounders in large comapred to small studies
My understanding is that in a randomised trial, one aim of randomisation is to reduce the chance of baseline imbalances (i.e. possible confounding factors) between groups.
Obviously known ...
1
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1answer
97 views
How to calculate the population survival probability in a two stage randomized clinical trial?
I am trying to reproduce a paper on two stage randomized clinical trials. In these clinical trials, a patient is randomized to either of the maintenance therapies $B_1$ or $B_2$ upon their remission ...
5
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2answers
65 views
Prejudice in blind test
There is a blind test that asks participants to distinguish Coke and Pepsi.
A participant will test 6 cups of drink and tell whether it was Coke or Pepsi.
Assuming that the participant can tell the ...
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0answers
53 views
How to choose which demographics to include in randomized trial regression?
I'm rusty on my stats. I am wondering what the prerequisites are for including covariates in my regression. I'm not looking for a prediction model but just the effect of the "treat". The sample was ...
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2answers
322 views
Why is random assignment important in stratified sampling?
Background
I raised this question because of an argument I am having with a question from user697473 here. The title of his question is "Formal definiton of random assignment." In the post he ...
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3answers
386 views
Random assignment: why bother?
Random assignment is valuable because it ensures independence of treatment from potential outcomes. That is how it leads to unbiased estimates of the average treatment effect. But other assignment ...
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3answers
205 views
Formal definition of random assignment
I am looking for a formal definition of random assignment.
Let $\mathbf{Z}$ be a vector of treatment assignments in which each element is 0 (unit not assigned to treatment) or 1 (unit assigned to ...
3
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2answers
275 views
How is approximately unbiased bootstrap better than a regular bootstrap with regards to hierarchical clustering?
I asked this question at BioStar but did not get a reply, so Im posting the question here.
What is a simple explanation of what an approximately unbiased bootstrap is with regards to hierarchical ...
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1answer
241 views
How to analyse RCT where significant baseline differences exist despite randomisation?
I'm analyzing a double-blind, placebo controlled RCT using an ANCOVA in R, where the predicted "treatment effect" shows up before the treatment has occurred!
The goal of the study is to determine if ...
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40 views
Testing single case result pattern against control sample
I have a single case result pattern in an experimental task (tactile localization with visual distracters and changed hand posture; hand(2) x congruence of tact/vis stimulation sides (2) x congruence ...
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35 views
Approach to testing difference from a bivariate null distribution generated by randomization
I would like to test if each of the red observations is more extreme in variable xy[,2] than 95% of a null hypothesis (black dots) generated by randomization.
I am ...
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131 views
Initial conditions of experimental units in Completely Randomized Design
Since I had no answer to the second part of this question I would like to ask it again providing some more infos I gathered in the meantime.
Context
We are designing a complete randomized trial in a ...
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1answer
108 views
Balance between randomization, interspersion and even initial conditions of experimental units
We are setting up a manipulative experiment in forest where we will test the effect of management on a number of health indicators.
We have 1 factor, 3 levels, 3 plots each replicated 3 times; ...
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0answers
112 views
Objections to randomization
In Clinical trials - a methodologic perspective, Steven Piantadosi writes (ch.13, p. 334):
In Chapter 2, I noted the objections to randomization by Abel and Koch (1997) and Urbach (1993), and ...
3
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2answers
220 views
When using stratified randomization in a RCT, how many envelopes per stratum should be prepared?
If one considers a hypothetical RCT, say a total sample size of 300, separated into three strata based on surgical procedure (open surgery, closed surgery, or combined procedure). Blocking in groups ...
