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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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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11 views
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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21 views
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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23 views
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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14 views
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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35 views
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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36 views
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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11 views
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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15 views
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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1answer
65 views
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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1answer
17 views
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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28 views
Contribution to Growth for a linear equation
I have this equation
$ Sales = Impressions * CTR * CVR * Price $
I know all the values for two different periods (January 2021, February 2021) and I want to know how much each components (impressions, ...
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1answer
86 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 (...
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How to measure whether change in one outcome predicts change in another outcome?
I am studying the effect of a self-compassion intervention on various outcomes (stress, anxiety, depression, etc.). I have pre, post, and follow-up data from my participants. I have already examined ...
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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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24 views
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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40 views
comparing historic pre-post student score averages with intervention group pre-post score averages
I want to see if there is statistical significance of improved posttest scores (DV) using IV (formative assessment) with my intervention group. We have never implemented before and give pretests and ...
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Statistical testing between two time periods to determine a change
I am trying to determine what model to use when testing how an index sector performance changes as we go from environment 1 to environment 2. The environment is based on changes in inflation and is in ...
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Test of normality with normalized change scores
We've done an experiment on the effectiveness of a learning intervention. We have two groups -- a control and experimental/test group where we had the participants do a pretest and posttest.
From the ...
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17 views
How to analyze treatment efficacy for small dataset
I have baseline and post-treatment questionnaire data on behavioural treatment and control groups. Each group has less than 10 participants.
I have missing data both on baseline and posttreatment ...
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14 views
Binary data of MCQ for paired T test
I am designing an experiment where I need to measure developer awareness after the introduction of a tool. basically taking 4 questions in pre and post-survey to measure increased awareness using the ...
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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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1answer
100 views
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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How to test if performance in Yr1 effects performance in Yr2?
I'm basically trying to compare whether students that perform better (eg; higher test scores) in yr 1 perform better in yr 2 (eg; still achieving the highest test scores). Students did 20 tests each ...
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1answer
193 views
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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20 views
About relative and absolute change
I am trying to assess the relationship of change in the level of a marker with the development of a disease. If I assess absolute change, there is a significant association. But if I assess relative ...
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7 views
Pretest posttest design with varying time between tests
I have a pre-test post-test design where several subjects were administered a drug. For each subject, I have $p_0$, a physiological measurement taken directly prior to the drug being taken, and $p_t$, ...
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15 views
What statistical test to conduct?
We conducted an intervention study (digital intervention) to understand the change in knowledge and various psychological variables (likert scale -- attitudes, beliefs, anxiety) on a group. We first ...
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21 views
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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29 views
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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1answer
236 views
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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1answer
488 views
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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Why we cannot take baseline as predictor for change in this case
It is generally recommended that baseline should not be kept as predictor if change is outcome variable. Explanations for this have taken both baseline and final values as random (e.g. see here). ...
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Keeping baseline as predictor with change score as outcome in this peculiar scenario
It is generally recommended that baseline should not be kept as predictor if change score ...
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825 views
Is there a mathematical proof for change being correlated with baseline value
It is shown in answer here and at other places that difference of 2 random variables will be correlated with baseline. Hence baseline should not be a predictor for change in regression equations. It ...
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1answer
77 views
Change Score or Regressor Variable Method - Should I regress $Y_1$ over $X$ and $Y_0$ or $(Y_1-Y_0)$ over $X$
I have data about investment preferences 1 year before the Covid and during the Covid lockdown.
Some changes appear using simple T-Test. I want to be able to assess if these changes are particularly ...
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1answer
111 views
Gain scores as an outcome in HLM?
I'm analyzing data from a single-group, pre-post design, trying to see if student beliefs change after an intervention. Students are nested in classrooms, and there is a significant amount of ...
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170 views
Creating Z-Scores for Meta-Analysis
I will be conducting a meta-analysis that compares post-treatment changes in depression between the control and intervention groups. I have the Mean, SD, and N for depression at both time-points. ...
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1answer
226 views
Why do regression models predicting a change score vs. predicting T2 controlling for T1 yield slightly different results?
I am running multiple regression models testing whether a change from T1 to T2 in my IV predicts a change in my DV (also from T1 to T2). I am running these analyses in R using the glm function.
I ran ...
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Comparing the before and after scores between two groups
In this experiment I'm trying to make, one group of people watches a lecture series and one does not. Before the lecture series, both groups' levels of optimism, knowledge, and anxiety are assessed. ...
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Latent Change Score modeling in Lavaan; Strict vs Scalar Measurement Invariance models
I am new to SEM and currently struggling setting up Latent Change Score models for testing for Measurement Invariance (MI).
I have a model with two latent factors (T1 en T2) with each 2 indicators (...
