Questions tagged [pre-post-comparison]
Comparisons before and after an event or experimental intervention. Includes BACI (before-after-control-impact) studies.
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Creating a standardized composite "score" made up of multiple continuous, dependent variables for analysis in SPSS
I am trying to evaluate how a surgical intervention (insertion of a spinal fusion cage), resulting in distance changes between two vertebral bodies, led to new symptoms (yes/no) in some patients but ...
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Treating multiple observed differences as a latent variable vs. difference in multiple latent variables
Suppose I want to model the change in some outcome before and after treatment. The outcome of interest is the change in a latent variable measured with error before and after treatment by 3 observed ...
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Can I still call this as a difference-in-difference analysis?
I have a regression which has treatment and control groups.
I want to test how the treatment group (binary variable) reacts during crises periods compared to control group.
The crisis variable is a ...
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Testing for normality of difference between pre-post scores
I'm currently trying to decide what test to run on SPSS for my data. I am comparing the effects of 3 different interventions on trauma scores. I have both pre and post-scores.I have created a ...
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How to evaluate patient significant improvement?
Imagine the following study where we want to teach a group of $N$ patients to improve their capacity to hold their breath under the water. We have data for the patients before teaching them and after ...
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Measuring before and after results of a treatment with N people and K trials per person
Let's say I have a group of 10 students and I want to study the effect of a treatment on their memory.
I will have them each take 20 indistinguishable memory tests. Then I will administer the ...
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Comparison of two groups without using interaction effect
David Spiegelhalter in Art of Statistics states the below analysis would be problematic. Can anyone give an example (real or simulated) of how this would be a problem?
Measuring two groups at ...
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Calculating Cohen's d
I have two groups (experimental and control) and a measure (an estimate of confidence) measured at baseline and at post-intervention. I have ran a multiple regression and found that the intervention ...
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How control for a pre-treatment outcome $Y_0$ if is a strong confounder while avoiding regression to the mean bias for treatment effect on $Y_1$?
I'm facing a dilemma in a pre/post cohort matching analysis for a healthcare intervention:
Matching on the pre-treatment outcome $Y_0$ (a continuous variable) will likely lead to regression to the ...
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Valid to run post-hoc tests on matched data or running afoul of Table 2 Fallacy?
After completing a difference-in-differences matched cohort analysis to estimate the pre/post treatment effect of a home health nursing intervention compared to a control group, my employers are ...
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Comparing proportions in dynamic populations
I have an example of dataset like this:
Members of insurance plan
01.01.2021
01.01.2022
<18 y. o
2100
3000
Total members
200000
230000
How can I compare proportions and define if proportion on ...
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How to identify variables
Good day. Basically, my study is about games' effectiveness between two groups. I have three assessments: pre-test and immediate post-test (to test academic performance) and delayed post-test (to test ...
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Significant difference among Nominal data
Suppose that I am interested in implementing a certain intervention to boost my student's reading frequency. I have the following fictitious data of 100 students, how will I measure if the ...
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Use Pre-Experiment Difference as Null Hypothesis Mean?
Traditionally, we assume that the mean of a null hypothesis is zero when testing whether two population means are the same. But in reality, no two population means will be exactly the same even if ...
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Is difference-in-differences dead?
There have been a number of papers over the past 40 years supporting either change score or regressor analysis for longitudinal observational studies.
However, recent papers (for example, Tennant et ...
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How to compare the socioeconomic status between two populations after applying multiple correspondence analysis?
I have two datasets of two populations (before and after)
with the task to create socioeconomic quintiles. Through many variables such as household assets and household quality, I used MCA (R language)...
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In a single-group observational study with change-from-baseline, is it better to model change itself or calculate it later?
Let's assume there is a simple observational study of patients. They are assessed at baseline and 5 timepoints, t0, t1...t5
I am asked to calculate the model-based (to account for all data) difference ...
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Moderation analysis with prepost control design
In my previous question I asked about mixed models. Now, I want to do a moderation analysis in the same context.
Recap: I performed a pre-post study with two Trainings (ViStra & LeStra), and I ...
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Linear mixed model, three groups, pre-post treatment
I have a dataset, which I believe is suited for analysis with a linear mixed model. However, I am quite new to linear mixed models and would appreciate some input.
The dataset includes three groups – ...
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Mean of individual percentage changes vs. percentage change of aggregated means?
Apart from the valid criticism of percentage changes, sometimes we are asked to use them by our employers or clients.
Let's assume we have 5 patients. Each has a pair of pre-treatment and post-...
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Slopegraph with too many observations
Currently, I am studying the book "storytelling with data - Cole Nussbaumer Knaflic" to learn about data visualization. Now I am learning why the slope graph can be very helpful. If you have ...
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Baseline-adjusted ANCOVA vs baseline-adjusted LME
I'm a bit of a novice at this so please be nice!
Essentially, I want to know which method is the most statistically sound in application. I have two groups (allocation), two time points (pre/post), a ...
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How do I model a paired experiment with pre-post data?
I have designed an experiment with 20K treated units matched to 20K control units. Every treated unit is matched to a control unit that is as similar as possible on a number of metrics.
The treated ...
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Compare change in two "groups" over two time points
I have two continuous variables: performance and expected performance, at two time points: baseline and after 1 year.
Furthermore, I have some potential confounders I would like to adjust for: weight, ...
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Causal diagram for difference-in-difference case-control study
I'm working on a matched cohorts difference-in-differences healthcare study with the following causal diagram:
where $X$ is the binary (Yes/No) nurse intervention identifying the treatment and ...
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When calculating a standardized change score, what do you divide by and why?
I understand that, in most cases, one calculates a standardized change between two scores as
(Lakens 2013)
i.e., the mean of the change scores is divided by the standard deviation of the change ...
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Repeated measures with nested data mixed effects model (singularity)
I hope you can help me. I performed a pre-post study with two Trainings (ViStra & LeStra), and I measured safety outcomes (e.g. Knowledge, attitudes, behavior, etc...) with questionnaires before (...
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Which analysis to choose for panel data with three timepoints? (Not interested in change but influence of other variable)
I have data from a 3-wave panel study which I don't know how to analyze. I am interested in how an independent variable (IV) affects a dependent variable (DV). Therefore, I am not interested in the ...
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How to incorporate repeated measures (pre and post experimental conditions) into three-way ANOVA?
I'm analysing data from an experiment I conducted last year with one treatment group and one control group, each imposed on two plant varieties in five pot sizes. I took two measurements from each ...
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Is it always appropriate to convert paired data to unpaired data?
This is a general question, which I have encountered regularly, but as it is seemingly very basic, I can not seem to find an answer / explanation for it.
Assume a situation in which we have paired ...
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Pre-post analysis on stores which do not start treatment at the same time
I have a control and experiment group stores where the treatment on experiment group stores doesn't start at the same time. I am thinking of doing a rmanova. But i am not sure if it's the right way ...
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ANCOVA with all continuous variables
I have the following variables:
Psychological trait data collected at pre- and post-intervention
Fitness data (e.g., weight in kg), collected at pre- and post-intervention
I am interested in seeing ...
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Does it ever make sense to use the sum of the pre and post measure means?
Say I quantitatively measure a specific trait of each of the students in a group so that each of the students receive a score. The average score of the group is $X_0$. After a treatment, I measure a ...
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Which test to use that includes repeated measures (pre and post) but also different treatments?
Currently looking at data in which each participant recorded their level of pain from 1-10 in terms of severity for both pre and post operation, for 3 different treatments. Such as the table below, ...
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Determine if treatment effect is distributed equally across participants in a study or driven by a few participants
This is perhaps a malformed question, but I'll give it a shot. Let's say I have a pre and post measure of some outcome variable and a dummy variable treatment that ...
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Effect sizes for pre-post control design but with uneuqal pre-post sample sizes?
I am trying to compute the effect sizes for the pre-post control design studies. Here is what I found in Morris (2018) and I quote
"For the PPC design, three effect size estimates have been ...
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Comparing sample fluorescence at different temperatures
First of all, sorry if this format of question has already been answered - but I've had a look at previous answers and still can't figure this out for the life of me.
So, I have these 15 samples of ...
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Mixed Model Specification for Change Analysis and Susbequent Mediation
I know similar posts have been made regarding change analysis, but I am unsure how to extend them to use packaged mediation analyses such as in R's mediation package (I am generally less familiar with ...
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How to compare -50% and +100%
This might seem (and be) a really trivial question!
I have this table:
...
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The right statistical test when you have a before/after + trial and control group
I am trying to understand what statistical test is best in circumstances where you have both a before/after (so paired data) and a control group
There are t-tests available for one of each scenario (...
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Comparing the Change in Size between Three Populations at Two Points in Time
I'm trying to measure the efficacy of a program that serves people experiencing poverty. We have data for the region that received the intervention, and data for two comparable regions that did not ...
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Does it make any difference to analyse change from baseline (observational study) or post-hoc contrast post vs. baseline?
I have an observational, non-randomized longitudinal study with 3 time point + baseline (t0 ... t3). Analysing solely the post-values in such trials is meaningless. I want to analyze the change from ...
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How to measure the change in customer flow from brand A to brand B at two points in time (pretest and posttest) after a stimulus?
I am conducting a research in which I have data on the purchase of 4 brands of some consumers in a first period of time (pretest). But I also have the data for the purchase of those 4 brands and the ...
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How to interpret a mediation where the a and b paths are significant, but the bootstrapped indirect aXb effect is not
I've run a parallel mediation analysis to test for the effects of a poverty simulation intervention. We have theorized that the simulation acts through changes to participants' internal and external ...
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Which tests to run for a population repeatedly measured both before and after a treatment?
I have an experiment with 10 environmental plots that will be measured for CO2 output daily for 3 months. At about halfway through the experiment a treatment will occur to 5 of the plots.
After the ...
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Comparing pre-test post-test results t-test normal distribution
Is the best way to compare the intervention group (n=32) with the control group (n=32) to do a t-test? I've got pre-test and post-test results and did t-test of both the pre-scores (IG compared to CG) ...
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On the defense of "change from baseline" even in randomized trials - can anyone question points in this article?
Many times I read a strong criticism on the change-from-baseline (adjusted for baseline or not) both in randomized and non-randomized. Several people advised "don't even think of reporting the ...
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How to form the hypothesis and which statistical test to use when we have before-after data of two individual groups?
So basically I have medical data where the data is collected from two different treatment groups and various variables are measured for individuals in the two groups. Data was measured before, during, ...
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Should I include covariates with a non-linear relationship to the dependent variable in linear regression?
In my linear regression model, baseline BMI is a significant predictor of BMI change following a weight loss intervention and including it improves fit (e.g. AIC). But it is strongly associated with ...
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How is it possible, that statisticians have OPPOSITE view on the analysis of change from baseline adjusted for baseline?
I always thought, that mathematics, thus statistics, are both strict sciences. So, two mathematicians cannot speak about the same topic and have contrary views on it.
In the pharmaceutical industry, ...
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