Statistical Analysis Stack Exchange
Statistical Analysis Stack Exchange

Questions tagged [control-group]

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

To provide a comparison in an experiment or trial it is common to have a group which is similar in all respects to the treatment group except for the fact that it does not receive the treatment. The control group does not necessarily receive nothing, for ethical reasons in clinical trials both groups may receive the standard care.

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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:…
dsbr__0
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Do we really need a control group when we can compare the treatment group with the status quo?

Here I am not talking about medical research, where there is placebo effect need to be controlled with the blind design. In social science studies, we almost never do blind experiment. In this case, if we have data from all the subjects, do we…
Feng Jiang
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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 have a conversion rate of 30%. I'm using a sample…
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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 collapsing this data down to daily data, a treatment…
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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: plants_lm <- lm(weight ~ group, data = plants) summary(plants_lm) Call: lm(formula = weight ~ group, data = plants) Residuals: …
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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, but actually he does it in a special way. He makes…
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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 cities to be the test group (i.e. intervention…
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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 be larger than the experimental groups by a factor…
Ali Shah
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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 more records for the Test Group. I would like to…
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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. What would be the best way to test if the…
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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: $Y_{it}$ = $\alpha$ + $\beta$ $(Leniency Law)_{kt}$ + $\delta$$X_{ikt}$ +…
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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 (baseline) and Tf (final). The number of participants…
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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 methods. Students in each participating class were randomly…
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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--------1000-------2.9% Variation…
Arpit Rai
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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 baseline values in control group ARE different from…
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