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Questions tagged [control-group]

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

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Dunnett's test for comparisons with Control - how to conduct ANOVA for 2 factors, as well as adjusting for different experimental designs?

From what I understand, before we conduct Dunnett's test for comparisons of treatments to a Control, we have to do ANOVA. However, for a 2-factor experiment, there seem to be a lot of problems to me. ...
MD P's user avatar
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Effect size calculation (with CI) for proportions with a 2-arm pre-post design (i.e. experimental and control group)

I've been trying to find how to work out the effect size of an intervention that has only provided information on the proportion of participants who reported they had increased 'knowledge' after the ...
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Difference-in-difference age groups

I would appreciate your help with a question I have. I'm creating a Difference-in-Difference study to examine how a conditional cash transfer to individuals 18 years of age to be spent in sport ...
Retir's user avatar
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Binomial test to establish a pass criterion

I'm sorry for the following -probably- stupid question. I'm performing a psychological experiment and I have no idea about how to establish how many control items one has to pass to be included. My ...
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Performing a Difference-in-Difference Analysis where the Control Group is Already Treated

I'm involved in a project where the outcome is the proportion of cancer patients who have received surgery. The treatment event is a state-level policy change that mandated moving all these cancer ...
user8408275's user avatar
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Is mutual exclusivity important for an A/B test for an audience selection method?

Say I want to measure whether a set of business rules is better than random at identifying customers most likely to respond to an email. The steps are: Take the entire population of 200 people and ...
djs's user avatar
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Propensity score matching for differently sized control and treatment groups

I would like to use propensity score matching to construct a post hoc control group to accompany a pre-determined treatment group. Some literature I am seeing says that I should pairwise match sample ...
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RCT with repeated measures help [closed]

I may be overthinking this and going down too many rabbit holes of possibilities, but can someone please help me figure out the appropriate ("best") method to use for this research project?? ...
J Carr's user avatar
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Baffled by Rubin's Potential Outcomes RE: What Would Have Happened?

Background Seeking a clear and authoritative explanation of a key concept of Rubin's Potential Outcomes Framework that is causing this hapless OP enormous grief. While the necessity to distinguish ...
Plane Wryter's user avatar
1 vote
1 answer
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Repeated measures - sort of?

I do mostly econometrics but am faced with a repeated measures type sample. I can solve it as a regression with dummies, but feel like I'm losing information in the repeated cases. I know the medical ...
UNDMac's user avatar
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Anova with a specific reference group? Dunnett's test overall p-value?

I have been trying to work through this idea for a few days now, and I think I am just really confusing myself at this point so thought I could hopefully get some help. The basic idea is, I have 1 ...
Jonas's user avatar
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Appropriate statistical test to determine if uplift between control group and multiple test groups is significant (pretest/posttest evaluation)

I'm trying to evaluate whether the difference in uplift seen in below table between the test groups and the control group is statistically significant. I'm unsure about the appropriate statistical ...
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DiD control treatment group choice

I need to evaluate the impact of the Labour-Intensive Public Works programme on social cohesion using DiD. I chose a set of control variables and an outcome variable. The thing is to choose the right ...
Карина Харченко's user avatar
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How to analyze a 4x2 design with an additional control condition?

I have a somewhat unusual study setup, for which I'm not sure how to analyze it properly. Basically, I have a 4x2 factorial design which assigns users to a condition A (4 levels) and at the same time ...
markusb's user avatar
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Can I use MANCOVA and SEM?

My project model includes one input variable, two mediators (both measured at the individual level, but one is about the team so rWG will be calculated), one moderator, and two outcome variables (...
Average student's user avatar
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I want to determine the impact of a policy on carbon emissions in a single country by doing difference in difference but don't have a control group

The policy was implemented all over the country and applies to everyone. Can I do difference in difference looking at yearly total emissions data of the country before the policy was implemented vs ...
Zee's user avatar
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How to control for mortality in an assay with multiple tests and inconsistent control mortality results?

Some context : I work on insects and most of our tests are mortality assays : we subject groups of insects, in replicates (usually 5-6), to insecticides and record the mortality 24h later. Since we ...
Throe's user avatar
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Three treatment groups vs one control group - only interested in comparing each treatment group separately to control - best test/follow-up test? [duplicate]

I have an analysis in which I have three treatment groups each assigned to a (different) experimental condition, and one group assigned to a control condition. I am interested in whether any/each of ...
Breathofthewold's user avatar
3 votes
1 answer
117 views

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 ...
user2974951's user avatar
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1 vote
2 answers
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How to analyze RCT with different number of measures with mixed models

I have data from a RCT analyzing the effect of an intervention on students. The experimental group had 3 measurements: before the intervention, directly after the intervention and six months after the ...
Laura's user avatar
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3 votes
1 answer
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Justifying a smaller control group in survey study

I am planning a set of studies that are interlinked. The first study collects information from 400 participants (exposure group), then some psychometrics are performed to assess the questions. In a ...
ReadBeard's user avatar
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Meta-analysis: Combining pre-treatment and control groups in different study designs

I'm working on a meta-analysis on a subject with scant literature. I'm analyzing changes in thyroid hormones in spaceflight, looking to see if there is a significant difference between pre- and in-...
Glassdyr's user avatar
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When you have a control condition, does it has to exactly the same way as the experimental condition?

So I am carrying out a research project for which I have multiple DV and covariates; A lengthy battery of questionnaires will measure these. I am wondering if, in the control conditions, I also need ...
Catarina Gaglianone's user avatar
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What is the best analysis method to use in a prospective study using wearable data (fitness trackers) to measure health parameters?

I have a prospective study where I need to compare the effect of heat (using an index) on health parameters (heart rate, sleep and steps) of a target population (for example adults with heart disease) ...
user366508's user avatar
2 votes
1 answer
664 views

Control group much much larger than test group

I'm a complete noobie in statistics and this is just me being curious about a study I read online. In the study they had 150 people who had tested positive for disease X, and a control group of 4000 ...
daniel's user avatar
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Comparing intervention/control group

I am planning to conduct a study which is based on an RCT design. I am intending to conduct an intervention. During this intervention, participants and control group enter some medical data on daily ...
Jens's user avatar
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2 votes
1 answer
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How does one define what measure to use for a Regression Discontinuity design?

For example I am looking at the effectiveness of a reading learning program for 3rd graders. How do I define an acceptable cutoff measure? Do I look at accepted reading assessment tests, such as ...
Ralph Winters's user avatar
3 votes
1 answer
39 views

Limits to how many control and treatment subjects may be paired in propensity score matching?

I'm working on a difference-in-differences project where we're matching up to 5 control subjects to each treatment subject using a combination of techniques to estimate treatment effects (ATT): exact, ...
RobertF's user avatar
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Difference-in-differences if the control group is treated later

Would a difference-in-differences analysis still tell me something important if the control group was treated later in time? Or, would I be better off only restricting my analysis to the time frame up ...
Abby S's user avatar
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P-value of chi-square test of independence

I need help understanding chi2 independence test scipy.stats.chi2_contingency. Let's assume I have two samples (of different sizes) of a categorical variable with 3 possible outcomes (1, 2, 3): Counts ...
kostek's user avatar
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Matching fixed control group to multiple time-varying treatment events so that each control is only used once/uniquely assigned

you have helped me tremendously over the past years and so far, I could find an answer to any the question I had! Thanks to anyone active in this community, I don't know what I would have done without ...
Leo I.'s user avatar
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Distinction between Treatment and Control Group

I am struggling to understand how to interpret the treatment and control group in the following case of DID regression. We need to estimate the causal effect of brick kilns on downwind PM2.5 monitor ...
Parul's user avatar
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2 votes
1 answer
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Identifying groups with better response to treatment

We have tested a population (splitted in test 50% and control 50%) with a treatment. Overall, the treatment was effective - our test variable was significantly different in the treatment and control ...
RMolero's user avatar
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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 ...
P_aza's user avatar
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3 votes
1 answer
221 views

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....
thando's user avatar
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3 answers
3k views

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: ...
Elasso's user avatar
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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)...
Christopher's user avatar
-1 votes
1 answer
104 views

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: ...
Adam's user avatar
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3 votes
3 answers
70 views

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 ...
robertspierre's user avatar
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2k views

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 ...
Anup's user avatar
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2 votes
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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 $T_j$ ...
David Draper's user avatar
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0 answers
12 views

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 ...
Brent's user avatar
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10 votes
2 answers
1k views

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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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: $Y_{it}$ = $\alpha$ + $\...
Phil Nguyen's user avatar
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1 answer
23 views

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/...
ila's user avatar
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3 votes
1 answer
1k views

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 (...
yer's user avatar
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1 vote
1 answer
30 views

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.
user320227's user avatar
5 votes
1 answer
182 views

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 ...
dsbr__0's user avatar
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0 votes
1 answer
28 views

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 ...
econo-whaaat's user avatar
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1 answer
209 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 ...
Peter Hacke's user avatar