Questions tagged [random-allocation]
The process of randomly allocating subjects (often in the context of a clinical trial) or other experimental units into two or more conditions.
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Is a high prediction performance of allocated treatment evidence for lack of unobserved confounding?
Example
Say Investigator 1 is looking to investigate the effect of fish consumption (a binary variable $A$ indicating whether they eat or do not eat fish) on cardiovascular health (a continuous ...
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What’s a good scale robust similarity metric?
Context: While designing an experiment, there is interest from leadership in pairing control and test units together such that every (test, control) pair are as categorically similar as possible.
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How do you use index cards to simulate a randomization sample for a "difference between two means?" (for data collected from an observational study)
I am taking an intro to stats course, and was wondering how I could use analogue tools (i.e. index cards) to simulate randomization samples for a difference between 2 means $\mu_1-\mu_2$.
For instance,...
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Using rerandomization/minimization for train/test splits?
When splitting data into train/test subsets, simple randomization will make the data distributions the same on average, but in finite samples, we may want to do more to ensure similarity. Stratified ...
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Why training is smoother when no randomization of batch after each epochs is applied?
I am wondering why training error converges more smoothly when I am not applying randomization after each epochs?
After each epoch I am taking the loss obtained in my last minibatch. I see that when ...
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Equal size random assignment
I am doing a ab test. I want to test if a treatment is statistically better than a control. I want to split 30 subjects randomly and evenly into two groups. My way is first generate random number for ...
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Balanced incomplete block design - randomizing treatment order
In a balanced incomplete block (BIB) design, what is the best way to ensure each treatment appears in all positions/orders? Should I randomize treatment order within each block, so that participants ...
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sample size calculation for binary outcome in multi-centre RCT
We are interested to see if an AI algorithm improves clinicians decision.
We know that treatment X is beneficial but there is a wide heterogeneity in the proportion of patients receiving treatment X ...
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Medical experimental design with non-comparable control
My population consists of people at high risk of cardiovascular disease who are identified through standard blood tests. These people, when identified, are prescribed some standard medication.
I will ...
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Help Needed for Outliers detection post paired T-test statistical test
I don't know if this is a standard way od doing things so open to any suggestions, basically I have done random sampling from my population to create 2 groups Treatment & Control. I also have few ...
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Stratified randomization: adjustment or not?
In randomised trials, there's a mantra saying "analyse as you randomise". So if I deploy a stratified randomisation, i.e. randomise within strata of some baseline variable, then this would ...
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Name for experimental design using randomization without replacement?
I have a between subjects design with 3 conditions A, B and C. My goal is to have 30 people in each condition. I have no other balance requirements other than the sample size being equal across ...
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What statistical design and analysis is appropriate for this single-arm study?
I have research to perform but I am not very familiar with statistical design and the relevant analysis that I have to do, but here is the idea of what I want to do:
It is a single-arm study, I have a ...
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Switching interventions after randomization
Suppose in a randomized control study, we assigned each individual to one of two interventions (A or B) with equal probability. And suppose for the sake of argument, there is complete balance in ...
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Intention to treat analysis for a non-randomized sample
What difference is there when applying ITT analysis to non-randomized sample data, compared to randomized data?
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Test statistics for randomization
I have a basic question on what method should be applied to obtain test statistics distribution.
I have two treatments $A$ and $B$. I want to test on mean $H_0: \overline{t}_A=\overline{t}_B$ as ...
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Right type of randomization / random allocation for low base rates
so I have a question on the correct "name" for the random-allocation to one of two treatment groups or one control group. We designed two interventions (readings material): one on ...
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Bootstrapping confidence intervals in randomization model and population model
Ernst 2004 shows that the permutation tests in the random assignment scheme (e.g., controlled experiment) and in the random sampling scheme (e.g., observational study) share the same constructing ...
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In a randomized trial, should we exclude random intercepts and use only slopes?
Let's say I have a longitudinal study, with patients assessed at several time points, which goal is to compare the treatment vs. placebo.
If, theoretically, I used a mixed model to analyse the ...
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AB Test, Experimental Design based on Machine Learning Output
Looking for the best way to set up an AB test.
Scenario is that the online product I am working with has logged in users that pay a monthly fee, and they can upgrade to get access to more features.
...
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Balance checking (using discrete variables)
Context
I'm doing a field intervention, with 4 treatments and 1 control. I have done a stratified randomization beforehand to ensure that demographic characteristics (gender, age, income group) are ...
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RCT using simple Randomisation, can extra participants be added?
I have been asked to perform the randomisation for a small RCT using simple randomisation. There are 100 individuals to randomise to one of two arms (control vs intervention). The researchers have not ...
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Inference for the average treatment effect for Bernoulli trial
In the book of Imbens and Rubin, they discuss four common classes of assignment mechanisms
that fit into this framework: Bernoulli trials, completely randomized experiments,
stratified randomized ...
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Are the arguments that placebo can be unethical mistaken?
There seem to be two ideas of placebo - or the treatment received by a placebo group:
A "simulation" of a treatment using saline or sugar pill so that subjects in a clinical trial can be ...
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preference between completely randomized or stratified/paired randomized design under covariate not predicting outcomes?
Consider potential outcome of $i-$th unit $Y_i=(Y_i(0),Y_i(1))$ with $0$ as control and $1$ as treatment and say $X_i$ is the only covariate associated to $i-$th unit. Assume $X_i$ does not predict $...
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Comparing treatments when there is imperfect compliance
Imagine a situation where we have a 2x2 cross-randomized program with imperfect compliance to the treatment arms. Thus, units are assigned to treatment A, treatment B, or both treatments. Once they ...
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How to forecast a rental weekly sales demand using a 4 year history data?
I need to estimate the weekly demand required for a specific product in a specific week at a specific location.
I have the past 4 years daily data of each product at each location.
For example: number ...
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Which test(s) should I use for RCT, 2 groups (intervention vs. comparator) and two DVs measured at multiple points (pre, post, 3, 6, 12 months)?
I am planning an RCT to evaluate the short- and long-term effectiveness of a CBT intervention.
There will be two groups: intervention vs. active comparator and two outcome measures: anxiety scale and ...
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Entropy balancing what are the gains in applying the technique?
I am developing a research that involves a model and when estimating it the coefficients were not significant. Because the hypotheses are strong, my advisor suspects that there is some problem in the ...
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My random allocation schedule list ran out - is it valid from a statistical standpoint to simply generate a new list?
Problem
My random allocation schedule list was design to randomize 100 participants. 50 participants have been recruited so far and randomized to treatment A or B. A recent change to the assumptions ...
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Current examples where randomized studies yield different results than observational studies
I have been reading the following paper by G. Smith (2002). I found it rather surprising. Some excerpts:
Promising epidemiological and laboratory findings led to a paper published in 1981 in Nature ...
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Excluding participants due to issue in randomisation?
I have been carrying a study and due to a human error in the randomisation process, instead of getting equal sized groups (I have 8 and aimed to have 100 per group), I now have around 90-100 ...
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Why is it acceptable to use the Sum of Squares of an Interaction as the Sum of Squares Error in a Randomized Complete Block Design?
Take for example the RCB design [Y = I + B + F + E], where...
Y is the response
I is the overall intercept
B is a blocking factor with two levels
F is a treatment factor with two levels
E represents ...
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What statistical methodologies are currently used in clinical trials to estimate treatment effects?
For example, are more novel methodologies for obtaining unbiased treatment effect estimates, like Targeted Maximum Likelihood Estimation, being utilized in randomized controlled experiments in ...
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What is a "split-body" RCT?
I am reading the RCT Wikipedia page, in particular the classification by study design.
There are described four types of RCT: (i) parallel groups (ii) crossover (iii) cluster (iv) factorial.
Then ...
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How many types of randomization are there? And how they each dealt with in the experiment's design or statistical analysis?
I am trying to understand randomization in experiment design, and am very confused, because there appear to be several types of randomization possible.
For example, for a Categorical Factor with Non-...
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Research design: Term for assigning participants to groups depending on day (instead of randomisation)
I am looking for the term used to describe when participants are assigned to experiment groups based on the day. We tested several classes in a training centre and selected randomly which class should ...
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Gender randomization in clinical studies
Hi i'm sorry if this has been asked before but I'm confused about the boundaries of gender randomization/distribution in a clinical study.
I have an example study of 430 participants with multiple ...
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Randomization method that allows for controlling for continous covariates
I have a group of patients (about 100 of them) that needs to be randomized into 2 groups (treatment and control) so that these groups were as similar as possible in terms of some (about 6-10) ...
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Dealing with pre-test bias by repeated random sampling
I'm dealing with zero inflated data that has extreme volatility. I wish to randomly assign X observations/participants/subjects from the data, treat half of them with a new treatment ("target&...
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What statistical model should be used to analyze data from a randomized pretest-posttest controlled trial when subgroups exist?
I'm planning a randomized pretest-posttest controlled trial of a psychological therapy intervention group compared to an active control group on a dependent variable of interest. My population will ...
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weighted randomization
I would like to randomize subjects in two groups so that the allocation ratio is 1:1.
Let's say the control group already has 5 subjects while the experimental group already has 7 subjects. Then, the ...
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Using an RCT and a retrospective cohort in the same study
I have seen that in RCT’s with very long follow up times the power of the study can be impacted by various factors in Herbet, Kasza, and Bø, 2018, and I was wondering if anyone has heard of comparing ...
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Is there a good framework for using Active Learning (reinforcement learning?) for Experimental Design?
We have a frequent problem that we deal with in a research environment that essentially boils down to finding the optimum conditions in a certain experimental space. At the moment we essentially solve ...
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Discover causal effects using OLS: does the treated and not treated group need to be similar on all observed variables?
I have one dummy variable, $D$, which equals 1 if the subject received treatment and $0$ otherwise.
My outcome of interest is $Y$. For example, $D$ tells me whether the subject took the drug or a ...
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Using PCA to combine variables in a randomized trial with a baseline and a follow-up measurement
Assume that $2n$ participants have several variables measured at two times points $t_1$ (baseline) and $t_2$ (follow-up). For illustrative purposes, I will use the example of just two variables: the ...
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Why use a stratified log-rank test if we balance over strata anyway?
When comparing survival data over time, we can use the log-rank test. An extension of this is the stratified log-rank test, which adjusts for variables.
Let's say we wanted to adjust for the effect of ...
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How to code a dummy variable for time in a difference in difference model in R?
I am trying to do a difference in difference analysis on data from a randomized controlled trial where the control and treatment occurred during the exact same time period (treatment was administered ...
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What kind of model to optimize the allocation a ressource in the context of time to event outcome?
I have a list of N patients that are competing for one treatment at each time. A treatment becomes available at times t=1,...,T.
I want to build a model that can take the time-varying characteristics ...
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How to combine observational and experimental data?
I’m trying to figure out the effects of system changes on user long-term revenue (over a 12-month period, say) for an online platform.
I have a lot of observational data, so I fitted a model that ...
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