# 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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### Can I conduct a paired t-test to compare regression coefficients?

I want to compare the regression coefficients for two variables from the same sample. My models may look like this:  \hat{Y}_1 = \alpha + \beta_1 * V_1 + \beta_2 * V_2\\ \hat{Y}_2 = \alpha + \beta_3 ...
16 views

### Comparing AUCs: Same Control, different Test Group - paired or unpaired? pROC

I want to compare two AUCs using a bootstraping method from pROC package (roc.test). I have done a classification using Logistic Regression: 1. Cancer (high risk) vs. Control = AUC 1 2. Cancer (low ...
20 views

### Checking for consistency and selecting the best among multiple measurement techniques

I am tasked with comparing $N$ statistical analysis methods (where $N$ is relatively small, say $N=5$), possibly not independent, for estimating some quantities $X,Y,Z$ based on some given data. Each ...
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### How to compare KM curves for paired data?

How can I use stratified log-rank test to compare survival curves for paired data? I can't find any R package for this. Thank you
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### Paired t-test for different observed parameters - Should I use multiple compairaison's tetsing and how?

I have a group of rats that each go through two treatments: Control (No stimulation) and Laser stimulation. For each treatment I obtain several number of parameters such as Attention score, number of ...
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### Classification with paired data

I have a set of data with predictor $X_{i,j} \forall i \in [1,N], j \in [1,2]$ for $N$ paired items in 2 classes. The full distribution over $X_{i,j}$ is not informative of class identity; however, ...
50 views

### Focal Predictions from a linear model: How to test for difference between factor levels (pairwise) instead of comparing errorbars?

Sorry for the cluelessness, I know this is a topic that arises often in different variations. Still, I couldn't find an answer for my situation. In my work, I sample people and try to generalize the ...
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### There is very slight difference but also statistically significant. Could there be a mistake?

In my study to investigate the effect of filter glasses on reading speed and contrast senstivity in albino patients, there is little change in the reading performance level n:61 patients Reading ...
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### What kind of test shall I use to test if the two data sets are significantly different?

The table below shows my example data set. I have 19 sentences (as an example). For each sentence, if word A is included it is recorded as 1; otherwise, it is recorded as 0 (shown in column A in the ...
22 views

### How to analyse association between two (paired) sets of measurements, when arbitrary to which set each member of a pair belongs

I have pairs of measurements and need advice to select a measure of association between the measurements. The special aspect that has me confused is the symmetry: there is no reason to allocate a ...
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### Entropy of large sample $X$ and small sample $Y$ comparison

Distribution $X$ of a real continuous random variable is unimodal and slightly non-normal with $1,000$ observations. Distribution $Y$ has the same characteristics (not perfectly identical in moments ...
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### Paired T-test or Linear Mixed Model or what else?

I have measured 8 different features on the same mice on three different days. I want to compare the means of those 3 days based on the features. I have executed paired T-tests for each feature in the ...
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### Should I treat the samples as independent or paired for testing?

So, I am going over the statistical testing that was done by a former intern and checking whether anything can be improved. I am having some trouble with deciding whether the samples for the project ...
11 views

### Comparison of time series data sampled on alternating years

I have a dataset of values sampled yearly from 1968-2018. I need to compare all even year samples(as a time series) to odd year samples(as a time series) to determine: if they do/do not follow the ...
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### Statistically different change

I'm a statistics noob, and I understand this is a very simple question, but I didn't know what to search for to find an answer. I have paired values for a variable (pre and post treatment) for two ...
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### Interpret results from Mann Whitney pairwise hypothesis test in R

I have run ten runs of cross-validation in R for four models, and I have then computed an RMSE error measurement on each run of each model. First, I used ...
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### Is it OK to use gls (Generalized Least Square) to analyze repeated data? What about the wrong degrees of freedom?

There are mainly 3 commonly used ways of analysing repeated observations via model: linear model via GLS estimation, generalized linear model via GEE estimation and mixed models (G)LMM. Let's forget, ...
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### 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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### Paired T test or some kind of ANOVA

I have measured left and right side bones of several whales. I want to know whether there is a difference between left and right sided bones. For this I have used a paired t-test. However, I also want ...
22 views

### Small paired samples comparison: which approach should I prefer?

I have the following small dataset, that consists of scores before and after a certain treatment for 15 individuals: ...
18 views

### how to test multiple models on the same data for significant differences

I have two sets of data that I am fitting 5 different regression model function types to: 2 polynomials, a power, an exponential, and a gaussian. I am using AIC scores to determine the best fit of the ...
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### Transform 3 dependent samples (each n = 10) into 2 groups (n1 = 20, n2 = 10) - which statistical test?

I have 3 dependent measures of psychological data (each participant took part in 3 different conditions). I would like to add sample 1 and sample 2 together (because condition 1&2 are similar) and ...
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### Is there a way to use Dunnett procedure to dependent, repeated data in a longitudinal experiment?

I have an experiment with 2 groups and subjects examined at subsequent times, t0 - called baseline - to t5. I would like to assess the changes from baseline and correct it for multiplicity. I know the ...
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### 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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### Which confidence intervals should I report in a pre-post and longitudinal trial?

Let's assume the following scenarios: Single group of subjects (1 within factor), 2 time points, pre and post. I report a confidence interval for the difference. That's simple. Two groups of ...
26 views

### Is adding batches of samples to a non-stat sig sample p-hacking?

Here's my scenario. I take 1000 samples each from my control and treatment. I note that the difference in means is not statistically significant (stat-sig) under the null hypothesis testing. I then ...
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### Comparing two absorption spectra as time series

I would like to compare two absorption spectra ( or interferograms) and conclude whether between these two there are statistically significant differences at particular wavelength intervals. At the ...
43 views

### Finding anomaly using statistical distributions [closed]

I am trying to find if a particular genre of books is more popular with people of a particular region of the world. I have data for the readership of a set of books of different genre corresponding to ...
103 views

### Distribution of the pooled variance in paired samples

Suppose a bivariate normal populations with means $\mu_1$ and $\mu_2$ and equal variance $\sigma^2$ but having a correlation of $\rho$. Taking a paired sample, it is possible to compute the pooled ...
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### Paired vs Unpaired t-Test basics

Hope this is not too basic: I understand we used paired testing in situations where, e.g., the same subject is tracked before- and after- an experiment/treatment, e.g., before- and after patient ...
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### What's the best metric to compare products that are defined by 2 parameters, where for both these parameters, lesser the value, better the product is?

Say the product is: house to buy. And, say, houses are defined by 2 parameters only: A, which is popularity rank (which is a proxy for the demand), and B, which is the price of the house Obviously, ...
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### Test for paired proportion data

I want to test for differences in the connectivity of two different brain regions (A and B) measured in 100 subjects. For each brain region, I have measured connectivity to 150 other brain regions (i....
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### Statistical Significance In Sample Between Two Time Points

I have a set of time series data with one observation per week for each county in a certain state. I want to see if there is a statistical difference between the observations at the point in time ...
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### Quantify the similarity between two sets of data

I have two sets of data y(x), one from experiments, and one from simulations. The datasets are naturally paired, as the same 80 different test set-ups were used for ...
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### Paired t-test with à priori known variance for Model validation

We have a multiple linear regression model $y = f(x1, x2)$, which has been fitted with measurements of a designed experiment of the input variables $x1$ and $x2$. Based on the design, the complexity ...
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### Paired t test: standard deviation of mean versus mean difference

I would be grateful if you could help me answering to a review I received: I have a sample that was evaluated in two different moments for the same outcome (n=80, normal distribution, Mean 1=272±20, ...
48 views

### Does a paired t-test compare means?

The reason I ask is that I keep reading it compares means, yet everywhere people keep using box-plots for visualization, which seems fishy to me. In more detail I would like to know whether ...
39 views

### Can I use a chi-square test to determine whether my samples are independent or paired?

I am conducting statistical tests for my current research project. Within the scope of this research project, I have two samples (divided by country clusters). The samples contain approximately 1500 ...
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### Should I choose single model A+B+A:B or two models A at 2 levels of B?

I have a longitudinal model: response ~ device * time. The device should lower the response over time. There are two devices: A and B. There is an interaction between the device and time. The problem ...
30 views

### Too small sample size for Wilcoxon signed rank test, alternatives?

I have a statistical question about my research. I performed photosynthesis measurements on leaves. I have 6 increasing light intensities, and for every light intensity, I measured the photosynthetic ...
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### Using Paired-t test for n > 30 non-normal difference

I have data from a paired experiment (each participant does both the control and experiment and we find the difference). I know that for the paired t-test, an assumption is that the difference is ...
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### What does, actually, the quantile regression asseses, assuming single two-level categorical covariate, difference in medians or median of differenes?

I know that, for a single, two-level categorical covariate, like sex={Male, Female}, the linear regression coefficients are about difference in means. It's like the t test. Does the quantile ...
46 views

### Is it appropriate to estimate the mean difference from a Wilcoxon p-value?

I am conducting a meta-analysis involving paired data (two instruments measuring the same thing). Original papers do not provide the standard deviation of the mean difference. One paper provides a p-...
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### Is it possible to calculate the standard deviation of a mean difference using paired data?

Is it possible to calculate the standard deviation of a mean difference using paired data (ie. two instruments measuring the same thing). Eg. I have mean1 and SD1, as well as mean2 and SD2. I know the ...
10 views

### Pairing conditions to run lmer

I have six conditions and would like to create three pairs of conditions, so that when I run lmer it compares conditions 1 & 4, 2 & 3, and 5 & 6. Here's what I have at the moment: ...
26 views

### How to test similar distribution of categorical data (k=3) between 2 paired samples

I'm looking for a test to compare the distributions of categorical data (3 levels: J,N,P) between 2 dependent groups (paired samples: question_1, question_2). We have 85 participants, each one of ...
107 views

### Why not include random slopes in a mixed model for a paired t-test

In class, we saw how one could use a mixed model as an alternative to the paired t-test. Lets say that we have subjects and each subject is measured twice. So we have a sample before (t = 0) and a ...
22 views

### Compare performance of libraries - test selection

I am trying to perform a comparison between three implementations of the same algorithm but using different libraries. However, I am not sure about my methodology. I am measuring elapsed time as a one ...