# Tagged Questions

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### Block randomization for different strata, how to achieve 1:1 treatment allocation

I am trying to randomize 60 patients in two treatments (A and B) where age will be used as strata. Since we don't know how many patients of each stratum will enter the study I have created two ...
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### 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 ...
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### How can I tabulate (data layout) the following randomized block design?

Suppose the experimenters are interested in how weight gain in rats is affected by different sources of protein: Beef, Cereal ...
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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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### 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 ...
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### 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 ...
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### 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 ...
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### 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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### 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 ...
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### 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 ...