Tagged Questions

5
votes
2answers
51 views

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 ...
3
votes
0answers
53 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 ...
17
votes
3answers
615 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 ...
0
votes
0answers
69 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 ...
8
votes
3answers
383 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 ...
4
votes
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 ...
7
votes
1answer
239 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 ...
2
votes
0answers
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 ...
1
vote
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; ...