Questions tagged [change-scores]

A single variable calculated from a variable measured at two different times (post - pre). Also called "gain-" or "difference-scores". Can also be used for other analysis of pre- and post- data.

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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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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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Analyzing data from a pre/post study when ANCOVA isn't possible and the denominator may be zero when calculating change scores

We have conducted an experiment on an animal model of a psychiatric disorder using a pre-treatment (PRE)/post-treatment (POST) design with two treatments resulting in 4 study groups (No treatment, ...
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Predicting behavioural changes based on absolute and change variables

I hope this is the adequate forum for my question. My aim is to predict behavioural changes --which are simply measured by a dummy-- following from changes in some characteristics. To do this, I have ...
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How should I statistically analyze pre and post test Likert scale data?

So I used a survey, where I had the participants answer 4 Likert-scale questions both before and after a presentation. Ended up with 7 participants total. Since I want to compare their responses pre ...
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Association between change scores of 2 ordinal variables

Given that much has been written against the change-from-baseline analysis, what would be a principled way to quantify the correlation/association between change scores of 2 ordinal variables? I still ...
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Meta analysis in R with changes from baseline scores: SMD interpretation and sample size selection

I have two questions regarding a meta-analysis I am currently running. 1. SMD interpretation for change from baseline scores In this meta-analysis, I have change from baseline scores and I am ...
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How do I calculate the mean and SD of change using mean and SD of baseline and follow up results?

I need mean and standard deviation of change from baseline to follow-up for inclusion in a meta-analysis. Some papers present the findings as baseline mean, SD and follow-up mean, SD for both groups. ...
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MIxed model on repeated measurements data with only 2 observations per patient?

I've been trying to find out if it would be possible to use linear mixed models on repeated measurements data when there are only two measurements within each participant. This paper (doi: 10.1002/sim....
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How would one analyze this study design (pre/post with waves)?

I have a study design to analyze. Users signed up for waves of a product I have pre/post measurements on each user Users were NOT randomized across waves such that users may differ by wave. The ...
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What statistics can I use in a case study to measure pre to post test changes

I am writing a methods section on technical refinement in sport. The study will be on a single participant (Case study) what statistics can I use to measure pre to post-test changes? I want to see if ...
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What ANOVA or any other test should I use if I have two independent variables and one dependent variable?

I have four groups - one group that will look at condition A, one at B, one at C and one is the neutral condition. The groups are comprised of different genders and age groups (ranging from 18-70). ...
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Kruskal Wallis on difference scores?

I'm wondering whether it's possible to do a Kruskal-Wallis test on difference scores, since I can't seem to find an example of this online. I think it would make sense conceptually, but I would like ...
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Pre-post model for ordinal outcome

I have outcome data collected at baseline and at one year follow-up. The responses are ordinal, with 0=better, 1=somewhat better, 2=somewhat worse, and 3=worse. My colleague is interested in seeing ...
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Tests for paired data

We have a paired data of before and after drug and placebo use and its effect on Systemic Blood pressure. The question at hand is " There is more than one way to make use of the baseline ...
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Modeling temporal change with 2 data points

Study Context: I am studying the relationship between a biomarker of cellular aging (telomere length) and menopause. We have 2 datapoints for a subset of the women. Therefore, our participants could ...
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Is it valid to categorize a pre-intervention score as the independent variable when the post-intervention score is part of the outcome variable?

I received a study proposal in which an individual wants to study the correlation between pre-intervention scores and post-intervention scores. As part of the study, all participants would undergo the ...
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Why changes of two variables are correlated but not the variables themselves?

I have two variables x and y and I measure this in two different situations, let's say pre-treatment and post-treatment. I have 8 values of x and 8 values of y pre-treatment condition and then I have ...
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Using change scores of one variable to predict change scores of another variable

I have data from a pre-post RCT that considered multiple secondary outcomes of various types (e.g. psychological, diet-related, sleep-related). I want to know whether the magnitude of change in one of ...
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Wilcoxon Sign-Rank Test with before/after treatment and control groups

Here is the setup of my experiment. I have 500 storefronts that are all part of the same chain brand. I've selected 250 of them to test an advertising intervention, and want to know whether the ...
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How to measure a pre-post change?

I would be very grateful for any advice on how to analyze the data of a small study I have conducted. The study has only one group of participants and their performance in a test was measured for 5 ...
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GLM Repeated Measures, with only two time-points (pre-post)?

I have a dataset that comprises of the same variable, measured at two different time-points (Pre-treatment and Post-Treatment). I want to check if there is an effect of Age in the results of the ...
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Repeated measures ANOVA comparing before and after intervention but has two types of "after intervention" conditions

I'm running a within-subject study that looks at subjects' performance before and after an intervention. In the study, subjects would perform a task (Task X), followed by a training, and then two ...
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How can i set up both paired and unpaired data for t test in SPSS?

My study involves a pre- and post-test knowledge score. However, due to participants not understanding the unique identifier code generation, some of the data collected is not able to be paired. Some ...
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How to analyze the effects of two treatments on two groups as measured by pre, post, and delayed post tests?

I taught two different classes using two different teaching approaches. Each class was given pre-test, immediate post-test, and delayed post-tests to assess their understanding of the topic. The pre-...
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Analysing before and after results of likert scale

I am a student with little knowledge on statistics. I ran a between subject experiment with 2 conditions, the control and test condition. In both situations I asked participants a set of 8 questions ...
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Data analysis with pretest and post test and control group in randomized condition

I have done a research on how stretching affect nurses' frequency of pain in different body regions and its pain score. However, I didn't recognized the intervention group and control group ...
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Compare pre-post change intervention across studies

I have got a question regarding the comparison of the effect size comparing a new (digital) intervention with previous data using a traditional intervention. In summary, we've designed a new (digital -...
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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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For counting participants should I use linear regression or poisson regression?

I would be very grateful if anyone with a stats background might sanity checks whether my approach is correct. I am recording the prescribing of a particular drug over time. Ultimately, beyond the ...
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Investigating effect of group on difference scores in mixed ANOVA

I was wondering what is the most elegant way to investigate group differences in change scores? Here's what I'm trying to do. Imagine there are three groups (a,b,c) where each participant is measured ...
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Interpretation when relative gain score is the outcome variable

I have two groups - treatment and control - and I am analyzing the effect of a policy change with multiple treatment periods. My dependent variable is a relative gain score (i.e. yt - yt-1)/yt-1). I ...
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Compare gain scores of two groups of unequal size and not normal distribution

I am trying to determine the effectiveness of a learning intervention that we developed. We had two groups, a control and experimental group, where we applied the intervention to the experimental ...
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Difference Score as Outcome Variable [duplicate]

I am trying to evaluate the effect of a certain policy on the achievement gains of students between two points in time. However, not all the students are exposed to this policy. I am supposed to use ...
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POMP score in a bidirectional scale

I am working with some data that vary along an arbitrary scale of -1 to 1. More specifically, this scale refers to a difference between two scores (with 0 meaning no difference, 1 being the maximum ...
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Appropriate regression model for a learning experiment on alpine skiing

We are running a learning experiment with a between-subjects design on alpine skiing: one group training according to an interleaved schedule whereas the other group train according to a blocked ...
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Confidence intervals of Cohen's d in controlled pre-post trials

The design with two sessions and two groups (treatment and control) is quite common. How can I calculate the confidence intervals for Cohen's d for that design? It is said that in this design we ...
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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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Binary outcome - what test

I am doing a study where I assess the knowledge of the same group of people before and after a teaching session. The question ask if the risk of developing cancer is higher or lower in the adult ...
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How to adress the -0.71 correlation artefact in the pre-post analysis of change from baseline in non-randomized trials?

Let me make some introduction first. It's well known, that in randomized trials, in the pre-post trials, by the formal pharmaceutical regulatory guidelines, both raw post and change scores should be ...
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Mean centering my data for regression

Can I mean-centre my data and then calculate the percentage change or is that redundant? For instance, I want to perform a regression on my data. I have my participants IQ score, which I mean-centered ...
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What is the best analytic approach for two arm randomized pre-post trial?

Study design is a classic pre-post design: two trt arms (treatment, control). Subjects are randomly assigned into two arms. outcome is continuous and measured at baseline and a follow-up time point (...
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Analysing change scores via linear mixed effects model with baseline adjustment?

I am still trying to find a model for a large dataset, approximately 1-5 measurements per patient (over time), one is the baseline value at t=0. The researcher is interested in the change over time ...
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