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2
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0answers
22 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
19 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
votes
1answer
37 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
votes
1answer
31 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 ...
1
vote
2answers
41 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 ...
1
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0answers
33 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
votes
3answers
564 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 ...
1
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0answers
43 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 ...
0
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0answers
3 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
votes
1answer
33 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
21 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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0answers
19 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
15 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
vote
1answer
25 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
27 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: ...
2
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0answers
12 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
votes
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
votes
1answer
36 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
votes
3answers
95 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
19 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
16 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
21 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
votes
1answer
112 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 ...
3
votes
1answer
114 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
vote
1answer
65 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
votes
0answers
27 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
votes
1answer
269 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
votes
1answer
48 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
vote
1answer
59 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 ...
0
votes
0answers
37 views

Can you exclude one country as robustness check in multilevel cross-country model?

I am conducting a multilevel study in which individuals are nested in countries. As a common robustness check in normal linear regressions, we can exclude one or a few countries with special ...
0
votes
0answers
25 views

Random Sampling Techniques

I have a pool of people who each have at least one email associated to him/her. Two people can also share a single email. This results in clusters of people chained together by email:person units. ...
1
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0answers
34 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
votes
1answer
2k 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 ...
0
votes
0answers
73 views

If 4 Peaks is GA-friendly, why is it getting stuck in a local optimum?

First, 4 Peaks: Given numbers N and T, an instance of 4 peaks,x, is an N-length bit string. We rate its fitness by doing o(x) = Number of leading 1s, z(x) = number of trailing 0s. An extra REWARD=N is ...
2
votes
1answer
469 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
votes
1answer
266 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 ...
2
votes
1answer
60 views

What is re-randomization?

I'm a statistics newbie, taking an online course, and the term "re-randomization" was thrown in without explanation. What does it mean?
3
votes
3answers
65 views

how to include distance buffers in cluster randomized trial

I need to incorporate distance buffers into the selection of treatment and control units in a randomized-controlled trial in order to minimize spillovers between arms. Cluster in this study is a ...
1
vote
1answer
109 views

Can confidence interval from hypothesis test inversion ever contain observed difference if that difference is significant?

My question concerns the method for constructing a confidence interval for a difference in means based on a randomization test (that can be found here , check under 'Confidence interval based on the ...
0
votes
1answer
99 views

Randomization software/service for clinical trial

I need a software/web-based system for the clinical randomization. This software/service should have the capabilities for handling stratification, multiple centers and block. The sample size of ...
1
vote
1answer
36 views

Is it possible for two independent people to generate randomness?

It is well documented that people are not very good at generating random sequences. However, is it possible that two people, working independently, could generate randomness together? Consider the ...
1
vote
1answer
195 views

How is the constant in Marsaglia's xorshift* RNG determined?

I get Marsaglia's basic xorshift RNG. For further randomness he suggests multiplying the result by a "suitable constant." This is some code I've found that does just that: ...
0
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0answers
34 views

Generating a dataset from mean, standard deviation, n and 95% CI

I have the output of a couple of Socprog models and I'd like to see if the results are statistically significant. Group A output: ...
4
votes
0answers
70 views

What kinds of PRNG exist outside Linear congruential generators?

I'm kinda running out of words, Linear congruential generator are really low quality PRNG but it was all I needed for some basic stuff, now I need to fill the blank and get to know other families of ...
1
vote
0answers
18 views

Correcting for multiple comparisons using simulated distribution

To check if unilateral pairs (defined below*) are coordinated (i.e. move together) in a flock of N coordinated individuals, we generate hypothetical (null) distribution of a certain focal parameter of ...
6
votes
2answers
470 views

Test the randomness (uniformly distributed) on a 64 bit float random generator

We have a random number generator which is supposed to generate 64 bit floats, uniformly. We want to test whether it is a good uniformly random. I am not asking the general way to test it, as it was ...
2
votes
0answers
74 views

Randomization test and comparisons of many to 1

I have about 80 different groups, each with 3 replicates which I would like to compare against a control having always a value of 1. As I have a low number of replicates and many groups having 2 ...
1
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0answers
28 views

Randomization Testing help

I am scratching my head over this one...any help would be greatly appreciated. I want to know if the average travel time between Guell Park and the beach in Barcelona using the bus or the metro ...
4
votes
1answer
43 views

Randomisation for 2 site clinical study

If I want to conduct a randomised study in 2 sites comparing two clinical treatment arms, and every site is expected to include 60-80 patients, is it acceptable to randomise every new patient with ...