Questions tagged [pre-post-comparison]
Comparisons before and after an event or experimental intervention. Includes BACI (before-after-control-impact) studies.
239
questions
1
vote
1
answer
32
views
Can I do a multilevel analysis for my study?
Some details about my design can be found below:
There are 2 groups: Group 1 and Group 2.
There are different numbers of people in each group.
A pre/post (measurement) of stress is taken several ...
- 11
1
vote
1
answer
40
views
On the success or failure of an experiment
Recently I've been asked this question and I wasn't really able to give a solid answer from a statistical standpoint. I hope someone can help me :)
Statement
Let's say that in a given region, in a ...
- 384
0
votes
0
answers
7
views
Anyway to transform data with a varying derivative into something that can give me comparative percent changes everywhere?
Sorry about the confusing title, I am so confused that I don't even know how to frame the question.
I have a device that gives me two sets of output values depending on how I set the surface charge of ...
1
vote
3
answers
85
views
How do i deal with change scores (negative and positive differences) as dependent variable in regression?
I am comparing the assessments of cognitive domains in 2 conditions: either in a noisy environment or in a no noisy environment. The same people are in both conditions. My next step is to see if there ...
- 31
0
votes
0
answers
9
views
Bayesian Modeling of Pre-Post Study with Counts Including Zeros in Baseline
I'm working with data from a pre-post study examining colony-forming unit (CFU) counts before and after the application of a disinfectant. My primary goal is to model whether there's a negative trend ...
- 2,733
1
vote
1
answer
44
views
Is it possible to get a correlation value greater than 1?
I am conducting a meta-analysis on a series of studies without a control group, with pre-and-postoperative data (Mean ± SD). I have calculated the SD of the mean change using the reported p-value ...
- 53
0
votes
0
answers
21
views
An ANCOVA pre-post framework for multilevel data?
I have a continuous outcome/dependent variable that is measured multiple times before and after an treatment/intervention per subject. The multiple measures are performed very closely together and are ...
- 133
0
votes
1
answer
30
views
Calculating SD for Change in time
I'm conducting a meta-analysis on weight change (T2 - T0) between Group 1 and Group 2. The data I have typically looks like this:
Weight (kg)
Group 1 (n=15) | Group 2 (n=14)
T0 65.31±16.49 | 59.06±...
0
votes
0
answers
14
views
Analysing pre and post intervention MCQ results for significance- which statistical test to use?
I have ran a teaching course for students. I carried out pre and post session MCQ quizzes to evidence effectiveness of the course, however the marks collected were anonymised (data collected via ...
1
vote
1
answer
102
views
Non-parametric test for comparing means of 2 or more dependent variables in R?
I have a matched paired dataset (student survey before a topic was taught and student survey after the same topic was taught) where I compare the means of their answers (answers are given in Likert ...
denise
0
votes
0
answers
16
views
How to analyze experiment with ordinal DV measured pre-post exposure?
I have an experiment with 3 conditions.
The dependent variable is ordinal (Likert style item on a 1-7 scale), and it was measured at 2 time points (before and after an event that all subjects across ...
- 1
1
vote
0
answers
39
views
What statistical test should be used for pre/post data (that violate ANCOVA assumptions)?
I want to assess the effect of a treatment (control vs. ash) on a continuous variable (e.g. calcium concentrations). I have two additional grouping variables that are also both categorical: location (...
- 11
1
vote
0
answers
12
views
In a causal diagram where the change score $\Delta Y=Y_1-Y_0$, does $Y_1$ cause $\Delta Y$ or does $\Delta Y$ cause $Y_1$?
In Shahar & Shahar (2010), the authors argue that in a typical pre/post observational study on two longitudinal outcomes $Y_0$ and $Y_1$:
the change score $\Delta Y=Y_1-Y_0$ causes the post-...
- 5,442
0
votes
0
answers
15
views
Help deciding analyses - RCT
I am developing a proposal for an RCT. The IV/treatment has two levels - active control Vs experimental treatment. I plan on measuring EEG ERP baselines as predictor variables for treatment response. ...
0
votes
0
answers
14
views
Estimating treatment effects, 2 Group Pre-Post Matched Analysis
I am trying to estimate the treatment effect for a pre/post w 2 groups design, subjects were measured on healthcare utilization 1yr before and after the intervention (non-random assignment). The ...
- 1
0
votes
0
answers
20
views
How to determine normalcy for a one group pre-test post-test? [duplicate]
My study is a retrospective one group pre-test post-test on multiple variables. Not every patient in the study had scores for all of the variables, so as long as a patient had both a pretest and a ...
- 1
0
votes
0
answers
39
views
Significance test for treatment when baseline of control and test groups are different
I have two groups of different sizes (control and test) and I want to measure the impacte of a certain treatment on the test group. Unfortunately, the control group has a different baseline compared ...
0
votes
1
answer
38
views
Statistical test for categorical data dealing with behaviour pre/post
I am looking for help with what statistical test I should use to analyse my data.
I want to know if there is a statistically significant difference between the animals behaviour before and after ...
- 1
2
votes
1
answer
70
views
Wilcoxon Rank Test Pre/Post By gender
I am trying to compare the paired pre to post-responses in a student survey to see if gender plays a role. I was told to do a wilcoxon signed ranked test, and I can get the mean and p-value by each ...
- 21
2
votes
1
answer
31
views
Interpreting coefficient of interacting factors to compare difference in scores from two time points
I am working with a colleague's data from a research project comparing two groups of learners on a test of language ability. Data are repeated measures, between-subjects. Participants in each group (M ...
- 23
0
votes
0
answers
15
views
confidence interval for the difference between 2 changes in proportions
I wonder if anyone can advise on how I can calculate a confidence interval for the difference between 2 quantities that are themselves a change in proportions. To be clearer if I have two groups (say ...
- 310
0
votes
0
answers
13
views
What statistical analyses would you use to analyze the change across two time points, months apart?
I will be administering an early literacy assessment to preschoolers at 2 time points in the preschool year. I want to be able to examine the growth from point A to point B. I also wanted to ...
0
votes
0
answers
60
views
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 ...
0
votes
0
answers
39
views
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 ...
- 691
3
votes
1
answer
77
views
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 ...
- 476
0
votes
1
answer
139
views
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 ...
- 1
1
vote
1
answer
42
views
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 ...
- 316
0
votes
0
answers
17
views
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 ...
- 111
1
vote
1
answer
100
views
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 ...
- 13.7k
0
votes
0
answers
69
views
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 ...
- 161
1
vote
1
answer
83
views
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 ...
- 5,442
1
vote
1
answer
41
views
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 ...
- 5,442
0
votes
0
answers
16
views
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 ...
- 31
0
votes
0
answers
25
views
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 ...
- 1
0
votes
0
answers
12
views
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 ...
0
votes
0
answers
13
views
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 ...
3
votes
0
answers
141
views
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 ...
- 5,442
1
vote
0
answers
24
views
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)...
- 243
0
votes
0
answers
26
views
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 ...
0
votes
0
answers
77
views
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 ...
0
votes
0
answers
85
views
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 – ...
- 1
0
votes
0
answers
46
views
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-...
1
vote
1
answer
64
views
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 ...
- 407
0
votes
0
answers
47
views
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 ...
6
votes
1
answer
118
views
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 ...
- 1,119
0
votes
0
answers
54
views
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, ...
- 79
2
votes
0
answers
92
views
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 ...
- 5,442
1
vote
1
answer
109
views
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 ...
- 211
1
vote
1
answer
139
views
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 (...
1
vote
1
answer
157
views
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 ...
- 13