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0answers
4 views

Allocation methods [on hold]

I have to allocate some observations into different clusters, maximating the omogeneity between groups. When a new observation arise, I collect some basic informations, let's say demographic ...
3
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1answer
39 views

When is there a point for using regression with controls to analyze experimental data?

Many randomized controlled trials in economics (and probably other sciences as well?) use regressions to analyze data obtained from experiments. In the simplest setup with binary treatment, assuming a ...
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0answers
23 views

How to use permutation test to create null distribution for categorical data?

Consider a population of 1,000,000 individuals. I have examined them all and identified 1000 samples which I believe are not like others. To confirm this I analyzed the 1000 sample regarding one ...
1
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0answers
35 views

Monte Carlo Methods

_I've tried using sqrt p(1-p)/n to get the standard error and then calculate the t test but for all parts I get a very large number of t so this means ...
1
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1answer
12 views

Randomization scheme for rating images and assessing inter-rater reliability

Apologies for the basic question, but I'm new to the area and I'm working on a research project on rating images, and assessing the reliability of these ratings, with the following structure: There ...
0
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0answers
28 views

t.test and permutation test results providing totally divergent answers

I have a data set with two classes and completely unbalanced samples sizes between the two classes. Note that even though I am showing some R code here, this is not a programming question. ...
2
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1answer
64 views

Suspiciously small p-values from randomization (Fisher-Pittman) test

How are p-values calculated when using a Monte-Carlo approximation of the Fisher-Pittman test? I was under the impression[1] that $p$-values generated by randomization tests should always be of the ...
2
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0answers
15 views

Experimental design: Same randomly selected stimuli versus different randomly selected stimuli in every subject

In an experiment, we’re going to present randomly generated stimuli to multiple subjects one trial at a time and measure neural responses to them. The stimuli are randomly generated to satisfy the ...
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1answer
37 views

Deep Neural Network weight initialization

Given difficult learning task (e.g high dimensionality, inherent data complexity) Deep Neural Networks become hard to train. To ease many of the problems one might: Normalize && handpick ...
1
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1answer
30 views

Can you acquaint a randomization test with any test?

I want to determine whether my randomizer works properly in a statistical test. One method to do this is a randomization test where we try all possible combinations for two groups. For example: could ...
1
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1answer
89 views

Chinese Restaurant Process

I want to implement Chinese Restaurant Process representation of Dirichlet Process for random partitions. The problem setup is as follows: I have some data (customers) which I have to randomly ...
0
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1answer
28 views

Randomizing Class Labels during classification to asses the feature selection results

I have a binary classification problem with thousands of variables and less than a hundred data points and class labels. The class is imbalanced (24 positive 51 negative samples). I have selected some ...
0
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1answer
15 views

Can a treatment have a significant effect on the sum but insignificant effect on its parts?

Using approximate randomization test, I show that my randomized treatment has a positive and significant effect on an aggregate index $Y_s$, which is the sum of 4 individual indices, i.e. $$Y_s = Y_1 ...
3
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0answers
78 views

Important question regarding feature selection methodologies in R concerning the randomness of the results

I'm currently testing some feature selection methodologies/algorithms in R, like the Recursive Feature Elimination from the R caret package, and also the RRF R package, to select a subset of features ...
0
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0answers
15 views

Randomization check: Using Chi-Square and ANOVA?

I many papers I find authors checking their randomization process (for experimental designs) with chi-square and ANOVA. I'm not quite sure what the authors did. One needs to control gender and age. ...
0
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1answer
33 views

Comparing two means (randomized experiment)

I'm kind of new to science :) for my thesis I worked on some study on health related behavior. There was an intervention for the experimental group and none for the control. So that seems to be a nice ...
2
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0answers
24 views

Effect of randomization of order of task complexity

I was conducting an experiment where participants performed a series of tasks; however, these tasks were in random order. Which test should I use in order to confirm (or deny) that randomization of ...
1
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0answers
21 views

How to test if randomization influenced the results?

I did an experiment where one group of participants answered questions using an existing tool and the other group my tool, which has some additional features. Everyone received 2 tasks, one complex ...
3
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1answer
52 views

Confidence Interval and P Value uncertainty for Permutation Test

I'm very new to resampling techniques. As I'm learning randomization tests right now online, there are two main questions coming to my mind: YES, it's easy and intuitive how p-value is computed with ...
0
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1answer
63 views

Estimation of sample size for stratified randomized clinical trial with R

We want to conduct a multi-center randomized clinical trial with two arms (2 treatments : a superiority trial) stratified on three centers (three sites). The primary outcome variable is a continuous ...
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2answers
42 views

I wanted a 10% chance of an item entering a queue to be marked differently, could I roll a 10 sided die and mark the item if it's equal to 1?

If I had an infinite stream of items entering a queue, and I wanted ~10% of them to be marked in a special manner, would it be "correct" to roll a 10 sided die each item that passed, and if the die ...
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0answers
42 views

Is this random or convenience sampling?

I have three randomised control trials to appraise for an assignment. Each have similar inclusion/exclusion criteria. The researcher has obtained the sample from a hospital (no mention of random ...
8
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3answers
581 views

Randomisation of non-random sample

I am always a bit surprised to see psychological adverts for participating in experimental studies. For sure, people who respond to these adverts are not randomly sampled and therefore are a ...
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0answers
44 views

Textbooks on Deriving Linear Randomization Theory Models (e.g., $Y_{ij} = \mu + \beta_i + \tau_j + \epsilon_{ij}$)

In the M.S.-level Statistics Methods class I am taking, I've learned about various linear models for experimental design. Take, for example, $$Y_{ij} = \mu + \beta_i + \tau_j + \epsilon_{ij}$$ for ...
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0answers
5 views

sampling size for binary group estimation (under randomized validation)?

Having binary groups with n members (size of several thousand or more members which can have 0 to ...
0
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1answer
47 views

Non-random assignment to treatment group due to anticipation of treatment in difference-in-differences design

I have a very basic question regarding a DiD-Design. If the subjects in this design select themselves into treatment/non-treatment group because they anticipate the treatment (e.g., they want to ...
0
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0answers
24 views

Treatment Effect Approach and Selection Bias

Suppose to have the National Health Interview Survey data (NHIS), the health status of the observed people as outcome $y_i$, which has got different potential outcomes on the basis of a treatment ...
0
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1answer
24 views

Placebo effect in randomized controlled trials (RCTs)

How does the number of intervention arms in a given RCT comparing several interventions to a placebo affect the placebo effect?
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0answers
16 views

Extract habituation effect with randomized trials

I want to find an orientation effect in my data. I did a response time experiment with 2 conditions (congruent and incongruent response mapping [answering a-left-b-right vs. b-left-a-right]) ... Now I ...
1
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1answer
32 views

Control variables in experiments

Assume you are trying to test the effect of condition X. You sample people randomly and put them in a manipulation group (condition X) and a control group (condition Y). Simultaneously you want to ...
0
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0answers
37 views

Non-Randomized Block Design?

Suppose I am running a $2^2$ factorial design in two blocks. Denote the factors as A and B and the four treatment combinations as $(1), a, b$ and $ab$. Consider the blocking arrangement: ...
3
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1answer
19 views

Adjust for covariables even in randomized experiments?

Randomization does not guarantee balance in an experiment. Balance is the prerequisite for causality, so theres a potential for using regression adjustment in randomized experiments. This is somewhat ...
0
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0answers
8 views

Dealing with “misfits” in stratified randomizations

Suppose we're doing stratified random treatment assignment. For the sake of this question I'm going to refer to the control group as one kind of treatment so, at the most basic level, we have 2 ...
2
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1answer
41 views

Experimental Design: Number of treatments and replications

I am learning about experimental design. I have been provided the following definitions: Factors: Variable(s) manipulated by researchers in order to observe response(s) Levels: Values of factors ...
4
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3answers
101 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
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0answers
21 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
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0answers
19 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
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0answers
26 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 ...
2
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1answer
144 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
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0answers
7 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 ...
4
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1answer
223 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
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1answer
72 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
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0answers
28 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
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1answer
291 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
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1answer
52 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
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1answer
63 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 ...
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0answers
38 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
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1answer
3k 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 ...
2
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1answer
638 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
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1answer
350 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 ...