Questions tagged [control-group]

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

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Using same control in two figures in a publication

I have a single experiment with 1 control group and 3 different treatment groups. I wonder if it is legit to plot the results in two or multiple graphs with the same control group. I am only ...
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Should I include the control group on a correlation matrix?

I have a dataset of variables from a control group (healthy subjects) and patients with a disease. Some variables are greatly increased in the disease group in relation to the controls, however within ...
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What is the best way to compare changes between two groups?

Given we have two equal-sized groups, each with a continuous pre and post-measure. E.g., in an RCT with a treatment and a placebo group and a pre and post-intervention outcome measure, and no drop-out....
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Best way to compare two treatment groups to a control

I'm trying to compare two different fertilizer treatments to a control group (no fertilizer). I ran a model like this: ...
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Binomial Proportion Test on test and control populations [duplicate]

I am new to statistical tests and request your help with the following question: A company wants to test the hypothesis that it's new ad will increase it's total number of subscribers (conversion rate)...
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What control should I use to compare to tumor growth in mice treated with IL-17A intratumorally?

I am conducting research to answer the question, at what concentration does esophageal squamous cell carcinoma begin using IL-17A for tumor proliferation? I plan to inject the tumors in the mice with ...
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How to select control group if I have limited data points

We're launching a campaign and want to see the impact in consumer behavior. This is the experimental group. For choosing the control group I was thinking into checking for past data to see which is ...
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Which tests should i do with a control group and a experimental group with pretest-posttest design ( 2 levels)

I have an experimental design with a Control Group and a Experimental Group, i have one pretest and one posttest ( 2 levels i think i´ts called) for 5 different variables. Which tests should i run on ...
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How to split a population in test and control group

I have a requirement to split a population in test and control group and we have to propose the groups in terms of percentages (i.e test = 80% control = 20%). For example: If I have a population of ...
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Determining sample size for comparing rate of occurrence between two groups

Scenario: You are running a comparative clinical study. A test product is being used by one portion of the population (Group T) and a control product is being used by another (Group C). The Question: ...
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In a RCT, what are the risk of selection bias if no allocation bias is present?

In the Wikipedia page about Randomized Controlled Trials (RCT), the procedures section states that RCT minimize selection bias and allocation bias. My understanding is that selection bias "occur ...
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Treatment group size vs. Control group size for difference-in-difference estimation

I am reading an unpublished paper that employs diff-in-diff to firm data containing a total of 2598 observations. Of these observations, 2474 are in the treatment group and 124 in the control group. I ...
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Testing in a model with lagged variables and control/treatment groups

Say I conduct regression: y ~ x + t + lag(y) Where y is the independent variable, x is some explanatory variable, t is a dummy variable denoting 1 if the observation is from the treatment group and 0 ...
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MCMC fitting of Dirichlet Process or Polya Tree prior to residuals in (simple linear regression)/(2-independent-samples) problem

Consider a simple location-shift semi-parametric model with two mutually-independent samples (in what follows, $F$ is a cumulative distribution function (CDF) on $\mathbb{ R }$, the $C_i$ and $T_j$ ...
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Using opted-out customer list as a control group for targeted promotions

I have a targeted email promotion list and I want to create a control group. My friend wants me to use the "do not contact/opted out" list as a control group, but I would think that those ...
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Analysing a controlled pre-post intervention study

I am conducting an analysis involving a non-randomised group of 30 individuals who received an intervention with the purpose of improving medicines regimes and a matched 1:1 control group as part of a ...
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How can someone improve a synthetic control?

This is a broad question, I know, but I feel like it's ok to ask because I searched everywhere and I couldn't find the answer. So I was studying about synthetic control (here: https://matheusfacure....
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605 views

How to plot the graph or perform a formal test of parallel trends for generalized DiD?

A. Background: Dasgupta, 2019, p. 2596-2597 create a baseline as below to study the impact of staggered design difference-in-differences (DiD): The baseline identification: $Y_{it}$ = $\alpha$ + $\...
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What is the RCT design where all participants get placebo first, then non-responders get randomized to treatment?

I'm trying to find a paper documenting an RCT design where all participants start by receiving the placebo only, and then participants who do not respond to the placebo get randomized to treatment/...
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How to calculate effect size for a pretest-posttest-control design study?

I am trying to calculate the effect size of exercise on depression. So I have 2 groups (control and intervention) in an RCT setting. I have both mean values and standard deviation of groups at T0 (...
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How to choose control groups (and how many) to use in CausalImpact?

I'm using the CausalImpact package and noticed that the results are very sensitive to the choice of control groups being fed. My main questions are: Is there a recommended approach for how to choose ...
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Does a large control group lead to violation of assumption made to use difference-in-difference methods

Does a large control group lead to violation of assumption made to use difference-in-difference method? The control group is around 10 times larger than the treatment group.
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Should I plan my AB testing accordingly to a minimum number of days or to the number of datapoints?

Here's the thing, I was planning to test a new strategy on my website. A typical AB test for a new homepage. One strategy is the current, the control; the other is the variant, the new strategy. I ...
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Control group participants

I have read a lot especially on RCT design but this hasnt been explicitly answered anywhere. Does the control group participants have to have 'opted-in' to the intervention and failed/not been ...
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77 views

Regression Model to obtain ATET

I'm working on a problem where I have two groups that both received a different treatment and one controlgroup. The total number of people in this experiment is 10,000 and the participants where ...
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114 views

Minimum sample size and power test

Suppose I have access to data on the energy consumption of a city with a population of 30000 persons. Imagine I want to test a new technology of smart energy, i.e if the energy consumption decreases ...
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Hypothesis Testing the difference in two means - Is N just the number in each group or should it also include each observation in each group?

I am working on a problem where I will be using a hypothesis test to find the difference in two means; a control group, and a test group. Each group consists of several stores where observations are ...
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How to compare score differences across time using unpaired data?

An anonymous school climate survey was administered to students in 10 schools in 2017. We have student-level data from that survey, which includes each student's overall satisfaction score (scale of 0 ...
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36 views

Control group within the country for national policy

I have a question about control group selection. I want to evaluate a private education suppression policy. The policy is that 70% of questions of a "national" university entrance test is ...
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364 views

Should the choice of propensity score matching versus weighting depend on the degree of overlapping of PS distributions?

I heard some opinions that matching is no good since it excludes some subjects. However, if we use PS adjustment or PS inverse probability weighting, is there a requirement on the degree of ...
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Is it worth redoing random split several times in order to draw the 'best' control group?

My customer performs targeted marketing campaigns on subscribers. For evaluation purposes he splits target audience into target and control groups (TG, CG). He says he does this splitting randomly, ...
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For retrospective observational studies how to determine the baseline of control subjects

I understand that for the active treatment group you can consider the start of treatment as baseline. How about the control group? It is difficulty to do matching without resolving this problem.
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Significant difference between randomized groups at baseline?

A collegaue and I are conducting a pilot study in a school, the aim of which is to assess whether an "alternative" educational tool is more or less effective than traditional teaching ...
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1 factor, 1 covariate, single control group. Is ANCOVA possible?

Let's say in our experiment we have three drugs (factor), each in 3 doses (covariate), with a separate group of subjects assigned to every drug-dose combination, and a single control group (no drug). ...
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Comparing the significance of multiple group frequencies in R

Suppose I have sum of frequencies from 4 groups with: ...
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791 views

What does 'control' in controlled experiment refer to?

Does 'control' in controlled experiment refer to: Having a control group for comparison, i.e "an experiment or trial that uses controls, usually separating the subjects into one or more control ...
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In what situations is a one sample T-Test superior to a two sample T-Test?

I'm trying to make a case for more use and respect of one-sample t-test in medical studies (which are generally looked down upon, wrongfully so imo). I see that in general medical studies prefer at ...
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322 views

Confidence interval around effect size for pre-test post-test control group design

I'm evaluating different experimental studies that all included an experimental group, a treatment group and a two measurements (pre-test, post-test) and usually report the mean, standard deviation ...
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How to compare 2 groups to show significant differences?

I am conducting an experimental study. I have 2 groups: The first group contains 3 healthy persons and the other one contains 3 patients (sick people). For each person of the study, we collect several ...
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514 views

Meta-Analysis without a Control Group

I am conducting a systematic review and meta-analysis which is investigating health-related quality of life in a particular patient population. I am having difficulties with conducting the meta-...
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163 views

How to measure Sales lift for a campaign without experimental design?

I want to be able to calculate Sales Lift for a campaign conducted but prior to campaign no control group was established. So, I cannot measure the impact on Sales because of campaign to treatment ...
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How to treat a duration of chronic disease

I have a data set that contains information about healthy dogs; dogs that have chronic heart disease; and dogs that have the same disease, but are considered as a long-livers. (All dogs in this ...
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654 views

Group By and Scale Data vs Scaling Data Without Grouping

I have a panel data set that covers 20 earnings dates for 50 companies. I would like to know if I should scale data by the ticker or just scale the data without grouping. What would be the pros and ...
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What is the name of the "test" for testing the similarity of control group and experiment group?

In a simple statistical analysis involving a control group and an experiment group, the research must demonstrate that before the experiment, the control group and the experiment group are the same or ...
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1answer
548 views

diff-in-diff with continuous treatment vs cut-off point (and 2 periods)

I have panel data for a number of counties for two years only (t = 1,2). The treatment, let's assume it's a policy implementation programme, happens in between year 1 and 2 and it is a continuous ...
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How to incorporate the customers leaving (addition of new ones) in the measurement of treatment effectiveness?

Consider I have taken a random sample for forming control group in month of January with sample size 5k and treatment group size being 95k. I am Sending offers to treatment group which are intend to ...
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2answers
123 views

Checking if treatment is effective without control group

I am experimenting with few treatments to see which one is effective. I do not have luxury of control group to compare against. In such scenario, is there any method to see if the treatment has been ...
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115 views

Two intact groups and independent sample t-test

The purpose of my research study is to measure the effect of project-oriented instruction approach on students' cultural awareness and their attitude towards the learning of foreign cultures. My two ...
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choosing a control as the *absence* of a condition in a retrospective longitudinal study

Let's say I am interested in cancer patients (or any other disease), and I am looking at their behavior prior to cancer onset - in a retrospective, longitudinal study. Now I want to design a control ...
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452 views

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 ...