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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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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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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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99 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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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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nested data, one type of measurement, t-test?

I have data with the following variables: mutant | wild-type, treated | untreated, and one type of measurements (size) for time point 1 and 2. The data is roughly normal. My ultimate H1 is that there ...
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23 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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22 views

Comparing groups? Wilcoxon, Paired test?

I am carrying out a simulation experiment where a fixed number of resources are, at the end of the simulation, divided between two groups of individuals, 'A' and 'B'. There may or may not be the same ...
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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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23 views

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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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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Test for Paired proportions

I have been asked to help a colleague analyze a dataset, and I'm having some trouble deciding the appropriate test to use. The dataset consists of 12 subjects who either succeeded or failed a number ...
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1answer
28 views

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
34 views

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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Help with a study-design for comparing subjective assessments using different methods

First post, so please be kind... Not sure if the forum is correct, but it was the best fitting on Stack Exchange, so here goes! The following situation is to be examined/evaluated, and I am at a ...
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Proper statistical method for comparing two annual time series of different measurements on same area

Lets say I have two annual time series - one is in-situ measured Sulphur input to given watershed and the second one is some index (number) acquired via remote sensing (satellite images) over the same ...
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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
53 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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107 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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30 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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56 views

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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73 views

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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49 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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review language please?

Our biostastistician is on vacation and im pulling my hair out. Can someone help me with a few things? I am comparing means on paired samples , i have six variables to compare means on. - is the ...
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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
19 views

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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25 views

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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300 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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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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81 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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143 views

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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60 views

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 ...
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Paired t-test with weights

I have $n$ pairs of observations $(x_1,y_1), (x_2,y_2)...(x_n,y_n)$ where each observation is itself the average over an underlying population: $x_1 = 1/N_{x_1} \sum_k x_{1k}$ $y_1 = 1/N_{y_1} \...
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ANOVA vs pairwise t-tests with multiple test correction

What is the difference between doing a multiple comparison test (e.g. ANOVA) vs multple pairwise comparisons (e.g. t-tests) with appropiate multiple test corrections?
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171 views

Paired sample t test normality violation

I would like to conduct a paired sample t test and thus, I'm checking for the assumptions of normality. Upon conducting normality testing, each group scores were found to be normally distributed ...
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Testing the difference of means of varying indirect measurements

I want to find out whether the means of $log(A)$ and $log(B)$ differ. However, instead of sampling $A$ and $B$ directly, I could only measure $c_1A$ and $c_1B$ in one experiment and $c_2A$ and $c_2B$ ...
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1answer
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What is the appropiate Non-parametric test for study with 3 conditions?

The IV has 3 separate conditions & the DV measures Pre & post scores (ultimately to see what condition has the biggest effect on the scores - if there is any). The data is non-parametric- ...
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Mixed effect model for data with paired/unpaired data

I have tested individuals on the number of parasites (ranging from 1 till 3) they have. For each parasite I described the severity of infection (ranging from 0.5 till 3). As an example, here a part of ...
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How do I compare two growth rates in a meaningful statistical way?

I have two growth rates (and also their corresponding levels) of two different groups for the same time period. I would like to show that: 1.) the growth rates were about the same for a specific month ...
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When to use raw (not relative) change vs. absolute change in a T-Test?

Suppose I have students 1 through 100 predict their test scores prior to taking a test. After the test, I record their actual scores, so that the head of my data table looks like this: ...
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Comparing observed and expected diets of two different species

My data consists of dietary data from two species (C1 and C2) and expected diets for each species (E1, E2) generated from a combination of variables, but is based on their foraging behavior. What I ...