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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27 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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20 views

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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15 views

Paired T-test for a population with positive and negative effects

I have before and after values where the treatment is expected to have a positive effect on a set of instances (I know what they ...
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2answers
48 views

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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8 views

How to compare treatment slopes in pre-post with 2 treatments?

I have a pre-post experiment. At t0 both groups start from a comparable values of some parameter. There are two treatments. Treatment A doesn't show improvement over time. Treatment B - does. In the ...
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55 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
35 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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12 views

Combined equivalence and difference testing

I have some data with two conditions, and a pre- and post-measure for each condition. I would like to know 2 things: That there was a significant increase from pre to post in both conditions, That ...
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18 views

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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28 views

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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461 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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13 views

Which type of analysis of the change from baseline is better: GLS + Dunnett on post values or GLS + ANOVA on changes?

Dears, I'm preparing for a project in ecology. We will analyse change from baseline as a reaction to some chemical substance. Let's assume the data will be collected like this: ...
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47 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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27 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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25 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
49 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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24 views

How to moderate a change score?

I am using STATA to perform linear regression. Here is the analysis I would like to perform: I have weight measured at Time 1 and Time 2 (continuous variable). I have fatigue measured at Time 1 and ...
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12 views

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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92 views

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 (...
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1answer
55 views

Controlling for baseline in difference scores

I have a dataset of participants receiving various frequency of intervention. We want to see if those who received more intervention had greater improvement between pre-intervention and post-...
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62 views

How to analyse pre-post ordinal data?

I collected pre-post data from a randomized controlled experiment. The intervention for the experiment group is an educational game and the pre-test and post-test contains 10 multiple-choice ...
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62 views

Can controlling for baseline in a regression with change scores be appropriate? (within-subjects design)

I ran a regression model with a change score (post minus pre manipulation) predicting my dependent variable. Initially, I thought it might be also interesting to control for the baseline score (pre ...
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26 views

Is there any formal guideline that would indicate the necessity for adjustment for baseline when analysing change from baseline?

As in the topic. I saw many critical discussions along with mathematical explanation on why the baseline shouldn't (or mustn't) be employed as a covariate, when analysing the change from baseline. ...
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8 views

Mean difference with paired pre- post- data, don't care about direction of change

I think I've confused myself into a corner. I have a pre- and post- measure, and the change is sometimes +ve and sometimes -ve. I want to see if there's a difference, regardless of sign change. What ...
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39 views

Is it valid to use a difference score between sequential timepoints as an independent variable in a longitudinal regression analysis?

Is it valid to use change scores, i.e. like change in body weight taken between consecutive time points in longitudinal analysis where I'm using nlme/gee? For example, bodyweight at hour 3 minus ...
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24 views

Descriptive statistics for 2 variables grouped by gender with spss

I have 3 variables one categorical gender and the others are the IQBefore and IQAfter which ...
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70 views

ANOVA/ANCOVA - how to analyse

In a basic research design where you want to test how some intervention (let's say our IV is 'drinking' with the categories water; sprite; and rum) affects some continuous measurement (let's say ...
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19 views

What statistical treatment should I use when comparing before and after likert scale data? (pre and post survey)

I have a 15 item survey questionnaire that will be answered by 30 respondents. Each item are statements about difficulty experienced, the entire survey measures the difficulty experienced by the ...
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11 views

Relative change of two vectors from a pretreatment value

I have to vectors $\mathbf{y1_{post}}$ and $\mathbf{y2_{post}}$ (post because they were measured after a treatment). ...
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16 views

Two Factor ANOVA with different sample sizes but similar variances

I gave an educational intervention to Spanish speaking and English speaking students. I gave a pre and post test to these students. Due to certain issues I was not able to identify students with their ...
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31 views

method for difference score prediction

I am currently working on a longitudinal analysis (with only 2 time measurements, T1 and T2). In this non-randomized data, I have 2 time measurements of fasting glucose as my outcome, i.e. Y1 and Y2 ...
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91 views

How to create a score for a SWOT matrix (strengths, weaknesses, opportunities, and threats)

I'm developing a participatory social environmental diagnostic. To do this, I'm using primary (qualitative data from interviews with stakeholders) and secondary data (local socioeconomic data). From ...
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26 views

Given a dataset of students' exam scores across 5 years, how can I determine what consists of a significant change in score?

Suppose I have the data below, of student's scores changes between 2013-2016 in : ...
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53 views

What practical use cases are there for the static group comparison design?

As far as I understand, the only difference between "the static group comparison design" and "the posttest-only control group design" is that the latter has randomized controlled trial (RCT), in other ...
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41 views

Is GEE a good replacement for ANCOVA to analyze change from baseline on 8-points Likert item?

I was asked to analyze adjusted change from baseline. The variable of interest is a customer answer reported on 8-point Likert scale, but constructed from numbers 0 - 8, rather than labels ("weak", "...
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1answer
58 views

Machine Learning alternative for hashing [closed]

Is there a Machine Learning technique that can used to detect the slightest change in data? I know this can be done using a hash but I was just wondering if there is any machine learning technique out ...
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1answer
19 views

Two formulas giving slightly different output

I am struggling to find a proper explanation why the two methods that I use for finding the difference in EXCEL are giving me two slightly different numbers. The idea behind the task is that we have ...
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3answers
338 views

Best way to compare changes in proportions

I am reviewing a manuscript so I cannot be specific but the authors had a treatment that was supposed to improve access to care. They had a treated group and a control group. Access to care was ...
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338 views

Bootstrapping ANCOVA to deal with violations of assumptions

I have a smallish data set with three randomised intervention groups ($n$s between 13 and 22), with pre-post variables. I want to run an ANCOVA with the pre-data as a covariate and post as an outcome ...
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1answer
51 views

Analysis of one group of subjects (data provided)

I have one group ($n = 39$) of subjects pre- and post-tested on a continuous variable. I also have a gender variable coded $0$ and $1$. I was wondering how I can analyze this data so to detect any ...
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119 views

Questions about conducting Mixed-Design ANOVA in R

I have a dataset that includes one IV with 3 levels (group 1, group 2, and group 3) and a repeated DV (pre test score and post test score). I am using R, but I'm unsure what codes I should use to test ...
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375 views

What test to be used for comparing pre and post test results with categorical data?

In the past month(s) I had to get familiar with statistics in order to validate my results although my background is computer science/programming. I currently examine whether I can enhance user's ...
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1answer
105 views

Which test is appropriate for comparing Pre and Post intervention data for an Intervention. Within Sample

Im running a study that tests whether an intervention is effective in reducing depression levels, increasing well-being, optimism and self-esteem and increasing positive affect. My DV's are: ...
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1answer
118 views

Unpaired or paired T-test when comparing before and after effects between two groups

If I have a drug purported to lower heart rate and I give it to a group of volunteers, I would conduct a paired t-test to determine if their HR before is lower than their HR after taking the drug. I ...
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3answers
4k views

paired T test: how to plot it?

What is the best way to represent a paired T test comparison for a sample with N=200 and 5 variables (only one of which is important)? nonpaired T test is not significant. A before-after graph is too ...
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1answer
474 views

Greater than 30% outliers in small dataset - what to do? Standard test? Test with outliers removed? Robust statistics?

I have a small-sample dataset representing observations from a longitudinal study. My principal interest is in 'change scores' across three parameters (A, B, C). This requires simple paired t-tests. ...
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110 views

Why not use baseline standard deviations to standardize effect size in meta-analysis?

in my meta-analysis I have studies with three kinds of data reports of RCTs which I want to integrate into one group with standardized effect sizes. studies reporting baseline and post-treatment ...
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211 views

Correlation analysis between two variables that each has pretest and posttest measures

Is it possible to conduct Correlation analysis between two variables that each has pretest and posttest measures? If yes, how? And if no, what kind of analysis should I be conducting? Edit: I would ...
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1answer
33 views

Assessing pre-post survey data with change scores?

I have about 50 pre & post-surveys for an intervention. I am limited to using excel and was told to only calculate the change scores. For example: ...
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83 views

using categorical variables in pre/post study

I have a continuous outcome variable, Y, that is a daily consumption score and want to study the impact of a policy change on a control group and 4 test groups t1, t2, t3 and t4. The policy change ...