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Questions tagged [control-group]

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In a comparative experiment a control group is one which does not receive the active treatment

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Different sample size of control and test groups

Hope someone can help my question: I have a survey study with one control group and one test group. Each is set to have 500 completes. However, we are short in sample in one group: Test is 350 and ...
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18 views

Is chi squared test of independence correct with control group?

I'm analyzing some data from an experiment in which passage of time between conflicting tasks is my independent variable and one of my dependent variables is a dichotomous one ("A","B"). I also have a ...
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Difference-in-difference analysis: more than one control group

I'm doing a difference-in-difference analysis of the impact of financial incentives on healthcare delivery. I have one treatment group (where there were financial incentives), and two separate ...
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8 views

Dealing with self-selection in the treatment group

I wanted to do a Randomized Controlled Trial for a new curriculum that was announced in my area. The issue is, certain teachers, under the organisation that I'm working with, have selected to teach ...
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11 views

Repeated measures with rotation of subjects within groups

I was wondering if you could help with the interpretation of a potential experimental design. We are testing two versions of a 'group' exam, score (out of 100) being the outcome variable, aggregated ...
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12 views

How to design inclusion criteria to match groups?

I am currently working on a study with a population of mostly veterans with chronic spinal cord injuries (goal n=60, currently n=27). We decided to add a comparison group of able-bodied controls that ...
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1answer
20 views

Before/After unpaired study with control villages analysed in R

For the implementation of a project, we have been following household access to services in two groups of villages, one an intervention group (I) and one a control group (C). Access as a Yes/No ...
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21 views

Measuring incremental revenue / uplift

I run a campaign with an experimental design setup. The target and control group is representative and split 70/30. The target group receives an email communication The dynamics of the campaign ...
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27 views

Standardization based on subsamples

I need to analyze data on the cognitive performance in a sample of participants divided into clinical (36 participants) and non-clinical groups (~100 participants). What would be the correct ...
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1answer
34 views

Splitting panel data into subgroups

I have a (an unbalanced) panel dataset of individuals over different periods of time (one time period = one month). I'm attempting to analyse the effect on the level of activity of the individuals of ...
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29 views

Pursuing meaningful questions about pre- post- intervention outcome measures in single condition treatment

If you are not fortunate enough to have a control group and have a single condition only, what meaningful questions can you ask about the change in pre to post intervention scores? If ANOVA or ANCOVA ...
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34 views

what happens when control groups results are larger than treatment group? [closed]

As a school experiment we had to modify a toy parachute and see if it increases its speed. We chose to change the toy parachutes material from plastic to nylon. We did Re-randomisation test 1000 ...
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1answer
34 views

comparsion of treatment groups based on different controls

I have experimental results from two days where I wasnt able to keep the same conditions from day1 to day2, so I have two sets of data: control day1 -- 2x treatment groups day1 control day2 -- 2x ...
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59 views

Are healthy patients an appropriate control group?

I am working on a study where patients with a chronic disease received a treatment. The goal is to determine the effect of the treatment on various outcome variables. I have pre and post data (before ...
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42 views

Control group selection

I am currently migrating some code from SAS to Python. I am trying to do the following in python: I have two groups of customers: those that were exposed to a campaign, and those that were not (the ...
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24 views

Pair-wise ANOVA or non-parametric comparison

I'm doing an experiment with 7 groups (batches) of 12 measurements of a certain chemical, where one group (b0) is considered the baseline case. The research question is to find out which groups have ...
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1answer
37 views

What is the Level of Evidence of “simultaneous self-controlled study”?

I guess this is an undefined thing, and would like to know your opinion. What is the Level of Evidence (as defined in the link by Oxford https://www.cebm.net/2009/06/oxford-centre-evidence-based-...
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1answer
139 views

Diff-in-diff with mactched control group

I want to run a diff-in-diff model. To choose an appropriate control group, I use a nearest-neighbor matching model based on several determinants of the outcome variable that I study. I was ...
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1answer
45 views

Diff in diff model with multiple treatments in multiple perdiods?

Can I estimate a diff in diff model to compare the effects of two different treatments that apply in different time periods in different countries? I have 30 countries for an average time span of 34 ...
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3answers
321 views

How to calculate the p-value of a test, that checked for a binary property?

16081 subjects were randomly assigned into two groups: test group: 7916 subjects control group: 8165 subjects Only the test group was exposed to something. During the test period 10 subjects of ...
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2answers
278 views

How to choose Control groups for Causal Impact algorithm?

I'm running an experiment and want to use the Causal Impact function to assess how well it performs. I have 10 different cities. I'm looking to find out what is the best method for choosing which ...
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1answer
41 views

Pre-treatment period in difference-in-differences model

I want to evaluate the consequences of a policy change using a diff-in-diff setup. I have quarterly data over ten years before the treatment ($t_{-10}$, $t_{-9}$, ..., $t_{-1}$) and ten years after ...
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31 views

Composition of groups in difference-in-difference models

Assume a difference-in-difference setup where the control and treatment groups are heterogeneous (different observable characteristics) but The parallel trend assumption is verified in the pre-...
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1answer
91 views

Meta-analysis in R without control group? Purely improvement of symptoms

I’m currently trying to perform a meta-analysis in R via the metafor package using data that does not have a control group. In this case, I am looking to see ...
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1answer
51 views

How to compare several means to control when the distribution is not normal and sample sizes are unequal?

I have a large dataset (n = 170,000), distributed roughly equally among 5 groups (each is 34,000 ± ~1,000). I want to compare whether the means in any of the first 4 groups are different from the ...
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60 views

How does using control variables in experiments affect the bias-variance trade-off?

Following up on the post, Using control variables in experiments?, I wonder how this connects with the usual bias-variance trade-off? That is, to minimise the MSE one must trade off the gain from ...
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9 views

Comparing a traditional and technology based tool

I am trying to compare a printed word dictionary with a digital dictionary that included added features like sound and video feedback. For this I have selected 60 participants and asked 5 questions (...
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20 views

Determining if a test measurement is from an empirical control distribution

I have a sample of 100 measurements from a control population. These measurements are not that close to a normal distribution. I also have made a single measurement that received a treatment. Is ...
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1answer
21 views

Test for significance before testing

I got a question regarding the binomial distribution and testing for significance in general. I need to divide a dataset into a treatment group (with phone call) and a control group (no phone call). ...
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1answer
38 views

Difference-in-Differences with Aggregated Data

I have access to aggregated data of a population for a 1,5 year period. I am interested in conducting an events study to check whether the implementation of a certain treatment will affect the ...
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1answer
38 views

Redemption proportion test: Big control group used several time or split into several control groups?

I'm preparing a test of proportions regarding a campaign redemption of several groups which have all common "demographics" but have been stimulated into different ways. At the same time I have a big ...
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31 views

Statistical test to use? [duplicate]

I am currently conducting a quantitative experimental research wherein 2 groups will be my participants. The research aims to determine whether or not Code-Switching is an effective tool to achieve ...
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1answer
47 views

Correct for cage effects using pooled control with ordinal response

Description of the dataset I have a data set with three categorical explanatory variable (treatment, environment, "cage") and an ordinal response (very low, low, medium, high,...). To control for "...
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1answer
28 views

Can I combine my controls?

I have an experiment with 4 conditions: control1, control2, treatment1, and treatment 2. Each has approximately the same number of observations. I want to perform a proportions test to compare the ...
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20 views

analytical methods for crossover study that has an addition control group

I have a crossover study where patients perform a cognitive task (with two conditions) when their brain stimulation is switched on and then off. Using a mixed effects regression, I would ensure that ...
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1answer
58 views

T-test , paired sample?

Regarding my data collection, I have five groups plus a control group. I need to compare each group with control condition with and then find the highest difference in one of these groups.To briefly ...
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1answer
203 views

In a multiple arm experiment, why does the control have to be larger than the experiment arms?

I am running a study with two experimental groups, each with slight modifications to their variables, and I want to be able to compare both to the same control. I have heard the control group should ...
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851 views

Size of control group and determining the winner of a multi-variate test

I am running a multi-variate email campaign with the following results: Version----------Users------Conversion Control Group----150--------2% Variation A--------1000-------2.1% Variation B--------...
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2answers
62 views

Calculate statistical significance when control is 0

My question for you guys is; I have a control group that are eating normal food and an experimental group that are only eating a western high fat diet. I wanted to look at how much the experimental ...
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244 views

Control group construction in Synthetic Control Method

I want to use the Synthetic Control Method to estimate the effect of the adaption of a new ballot institution (treatment) on fiscal policy. My sample consists of 20 units observed at 100 time points. ...
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49 views

Test to compare different subgroups when using same control

I am interested in finding out if the effect sizes between subgroups are significant are not. Here's the scenario: I have performed Analysis 1: Controls vs. Disease Now, Disease is subdivided into ...
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178 views

Determining minimum required sample size for control (for purposes of measuring lift)

SO in a sales setting where people can either buy or not buy (i.e. binary response), say I have a treatment that I know (or believe strongly) to be effective. I want to give it to as many people as ...
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171 views

Defining the size of control group in chi square statistics

I'm trying to compare the prevalence rate of autism in offspring of mothers with and without gestational diabetes. I gathered data from 1000 women, 8 children have autism (prevalence rate 8/1000). ...
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1answer
1k views

How to analyze this pre-post control-intervention data set?

I have control and intervention groups (N = 50 and 75, respectively) for whom 15 tests (all having quantitative results) were done at baseline and at 3 months. It is not a randomized study and the ...
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2answers
57 views

Use of words “control” and “test”

There are 2 groups of people, group A and group B. The groups were NOT assigned randomly and are not the same size. It is true that group B has a higher rate of success than group A, but this was ...
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1answer
326 views

Choosing Location Based Control Group

I have a dataset that tracks activities at particular locations. The dataset is essentially, timestamp, latitude and longitude, indicating an activity at that lat-long and that time. I plan on ...
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2answers
2k views

How to select a control / comparison group?

Lets say I'm creating a study that looked at treatments for metastasis in African American colon cancer patients. Would my control group or comparison group be Caucasian colon cancer patients with ...
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184 views

Siginificant size for a Control Group

I am designing project which requires me to select a Control Group. One the business requirements stipulates that I select as small a sample size as possible for the Control Group so there will be ...