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Questions tagged [paired-data]

Paired data arise when an experimental or observational study design deliberately samples two units as a dyad to form a basis of comparison. Use this tag for any question about paired data or their analysis.

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Algebraic Manipulations in Mann-Whitney-Wilcoxon Test Statistics

Given Let $\Delta > 0 $ be positive real number. Consider the Wilcoxon-Mann-Whitney upper tail test $H_0: \Delta \leq 0 \,\,\, \text{vs} \,\,\, H_a: \Delta > 0$ aimed at testing the difference ...
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Trying to do a paired t-test but one variable is not normally distributed, log transformation did not work

I am trying to do a paired t-test but one of the variables is not normally distributed (vegetarian enhanced), as you can see from the boxplot. I tried to do a log transformation but it made the p ...
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2answers
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How do you perform Wilcoxon matched-pair sign-rank test in Stata using a grouping variable? [closed]

I'm performing a diagnostic method comparison study in which I have 2 groups; one assessed using the experimental method, and one assessed using the standard method. These groups are matched, with 3 ...
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1answer
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Help with calculating number of animals for a fetal surgery experiment

Rather odd question. I'm a surgical resident who is currently a research fellow in a lab studying fetal surgery. Our plan is to test a glue which we believe will help seal a uterus after we open it to ...
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Proof that the pooled sample variance is biased when paired comparison is not used when it should be

Given the model for what is meant to be a paired comparison design: $y_{ij} = \mu_i + \beta_j + \epsilon_{ij}$ $i = 1,2; j= 1, 2, ..., 10$ Eg. An experiment comparing the different in mean hardness ...
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Comparing 3 groups at 2 time periods

I'm analysing a dataset and comparing three zones at two points in time. The data in question is: Hourly sightings of wild fish (CPUE) In one of three adjacent zones (A, B, and C) During the ...
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Applying Cliff's delta to paired data

Wikipedia provides a few ways of calculating Cliff's delta - an effect size quantifying distributional shift. However it only talks about having 2 samples that are unpaired. While one can apply the ...
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Comparing changes in pre-post count results for two cohorts

Thanks in advance! I have a pre-post analysis Of cases and controls. The outcome variables of interest are emergency room visits and hospitalization visits - both rare occurrences with median = 0 ...
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2answers
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Clustering for pair-wise data

I have been looking for algorithms in Python to create clusters from pairs of data. The data structure is similar to the stackoverflow post: An algorithm to create clusters from data pairs in python, ...
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2answers
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Should I use a paired sample t-test to compare two methods of measuring absorption lines?

Background I'm doing a research project in astronomy and measuring equivalent widths of absorption lines using Gaussian fits from a star's spectrum in order to determine the star's chemical ...
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Comparing survival rates

The question I have is focused on comparing remission rates at a fixed point in time. For example, I have cancer type A and cancer type B (the two are not mutually exclusive groups) and all patients ...
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1answer
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Which statistical test to use? Not really paired, not entirely unpaired

I am setting up an experiment where I would like to determine whether there exists a difference between the participants' average self reported mental effort in some condition A and condition B. The ...
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Regression on a change between a variable before and after?

In my dissertation I am using a paired sample t test to see if there is a statistically significant difference between consumers' intention to purchase from and attitudes towards purchasing from a ...
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Power of the test

How can I calculate the power of paired t-test if the null hypothesis mean is equal to 0. With a standard deviation 0.0373, sample size n=12 and alpha 0.05.?
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Is this an appropriate use of a paired t-test?

I want to compare multivariate gene expression data (1000s of genes) from two different conditions. I have three samples from each condition and the samples were collected in pairs on three different ...
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19 views

How to derive SD from difference in means in paired data?

I am doing a meta analysis, so I am collecting data from manuscripts. I need to obtain the mean and standard deviation for timepoint 1 and timepoint 2 for a variable called mpg but the paper only ...
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1answer
48 views

Paired t-test following main effect of mixed model with missing data

I am analyzing data for a repeated measures study with missing data. For example here is a 3 X 3 experimental design with three conditions and 3-time measures: I am using a mixed model for the main ...
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Comparing the subgroup to the group

I would like to compare the demographics of a total cohort of patients to a specific subgroup to see if there are differences. Since the subgroup of patients is included within the total cohort - what ...
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1answer
102 views

Mixed model applied to transformed data, or paired t-test applied to subject-medians of untransformed (skewed) data?

I am attempting to find the most appropriate way of analysing a set of skewed data, and I'm torn between two different approaches (each approach appears to offer its own advantages and disadvantages). ...
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1answer
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Use paired t-test to compare mean scores of 2 interventions, if 1 group got only 1 and another got both?

Let's say there was an intervention delivered using method A and method B. There was a post test asking participants about satisfaction on a Likert scale immediately after each method was delivered. ...
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56 views

Wilcoxon Signed Rank Test in Python (Reporting Siegel's T vs W?)

While using the Wilcoxon signed rank test in scypy over a subset of populations, I noticed that my test score was reported as zero for an array of differences whose distribution of medians is heavily ...
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Correction for different number of sampling days with individual samples for paired t-test

I have pre and post-fire data from GPS collars. Unfortunately, not all animals were collared at the same time and none of the animals were collared any more than 25 days before the fire. For each ...
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Alternative test to paired t-test? [duplicate]

I need to compare data from paired groups, but my distributions are non-normal, and my sample size is small. Are there any tests I could apply? I've been looking into non-parametric alternatives like ...
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12 samples, split into 2, 68 variables measured; 68 paired T-tests?

I collected blood samples from 12 patients. Each sample was split into two different storage vessel (24 total aliquots). All 24 aliquots were analyzed for 68 elements. Since the patients are selected ...
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1answer
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merit of t-test vs repeated measures

In a cohort study, patients have been enrolled for a new method of treatment of a condition. The measurement of interest, for example, tumour size is taken at baseline (BL) ie before treatment, the ...
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Kolmogorov Smirnoff test result vs paired t-test result

I have a set of medical data which contains two samples taken in different time periods. Although the samples do not strictly contain the same people in each group, a large proportion in each group ...
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Before and After mean difference with positive and negative changes

I have a table of data. Column 1 Before Column 2 After In some cases the After values are larger than the Before and vice versa. If I calculate the difference between each Before/After pair some ...
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1answer
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Comparing the results of 2 different type but identical samples from 2 devices

I have 2 columns of of the concentration of fat in fish which is measured by 2 different labs. I need to know if the difference of the results from these 2 labs are statistically significant. The data ...
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1answer
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Paired t-test of a non-normal data with sample size 66

I have a paired data with n=66. I understand that normality condition of differences data should be met to conduct a paired t-test. However, from the histogram, it doesn't appear so normal. The p-...
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One-tailed test for comparing paired dichotomous responses

Given reference samples $R_i$, I have two dichotomous responses $X_i$ and $Y_i$ I wish to compare. Each dichotomous response (relevant vs. irrelevant to the reference $R_i$) is generated by an ...
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1answer
54 views

Follow up medical study with missing data

I am analyzing some patient data for a medical study that has a duration of several years. Once a year, the patients are expected to visit the doctor, where they get four treatments, say A, B, C, D. ...
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1answer
342 views

emmeans pairwise contrasts result in same output values for all?

First of all, I am a beginner at mixed models, so I beg your patience and advice if this post could be improved. The structure of the data: ...
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31 views

Dependent variable as MEAN of proportions- treat as continuous?

I have two dependent variables, one is a mean percentage and the second is a mean duration. I understand that if your dependent variable is a proportion, you cannot treat it as continuous, for example....
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1answer
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t-test or paired t-test to detect drift for suicide prediction

Context and data I am studying suicides among the military. I created a table that aggregates certain metrics (number of holidays, number of hours worked, etc...) for each officer, for each month ...
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Paired samples t test in Python

I'm trying to conduct a paired samples t-test in Python (statsmodels package), but I don't see a function for it in their documentation. The closest I can find is ttost_paired, but I don't think its ...
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Analysing pre-and-post intervention study with anonymous responses

The study I am analysing is a pre-and-post intervention questionnaire of students' views before and after studying a module. The questionnaire was distributed in three different geographical ...
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Paired tests for one-to-many matched observations

I have a propensity score matched data after 1-to-2 matching. Each treatment case is matched to one or two control cases. May I use paired tests to compare the outcomes? The discussion https://www....
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1answer
56 views

Paired t-test or repeated measurement

I am designing RCT in the same patient (treatment on one side of the face and control on the contralateral side of the face) The RCT will be 1 month long with measurements happening at 2 and 4 week ...
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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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1answer
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Which test to compare Vitamin D serum level between malignant and benign tissues

I have Vitamin D levels for both malignant and benign tumor types and I need to compare them. Which test should I use, unpaired t test ? Another question; I have also PSA level ( also continuous data ...
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Which statistical test to determine interaction effect?

I conducted an experiment to determine the effect of blood type on blood cell interactions with proteins of differing blood groups and want to determine if there is an interaction effect for the ...
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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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General Procrustes Analysis - Appropriate Statistical Test for Repeated Measures

I have a question regarding General Procrustes Analysis (GPA) and was wondering if anyone has any advice. I am trying to test whether my data collection method is replicable between researchers. I am ...
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testing for difference in means across N pairs of samples

I have N different populations. Within each population, I have an equally-sized pair of sub-populations: $(t_j, c_j)$ for $j=1,N$ For each pair in each population, I have the measurement of a mean. ...
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Kendalls u-coefficient to calculate overall consistency of pair comparison experiments

I have 8 conditions. In a pairwise experiment, I am comparing 28 pairs: condition1 vs condition2, condition3 vs. condition 4, condition1 vs condition3, condition4 vs, condition2, etc etc. Each ...
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What test should I use with a non-normal distribution?

I'm working in a small project but I've a problem trying to choose a statistical test to use. I want to contrast the fetal death rate (Total fetal deaths/Total pregnancies) between 4 regions of my ...
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1answer
109 views

Different (Welch's) ANOVA tests and post hoc contradict paired tests. Which one to accept?

This is a problem that I think nothing would help but sharing my data here. I have 3 groups (n=7) which are paired. They are concentrations of a chemical compound in different parts fish tissue. For ...
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How to simulate data for generalized estimating equations (GEE) with logistic link function?

I am working with a pre/post test structure, measuring dichotomous outcomes. I am using GEE to estimate the coefficient for time (also a binary variable, 0 representing pre and 1 representing post), ...
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Are the results of my paired tests false positive?

I am dealing with a strange situation which I hope you can come up with a solution. I have 3 pared group(n=7 for each) which I tried to see if they are significantly difference and if so, in which ...
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Which test should I use to compare two binomial variables measured in same subject?

For example, let's imagine I measured two binary variable in my subject: 1) SUV or not SUV, 2) Speeding or not speeding (similar to a 2x2 contingency table). Let's say I hypothesized that SUV are less ...