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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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, ...
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37 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 ...
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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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20 views

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 ...
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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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1answer
48 views

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 ...
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2answers
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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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Using R. Two groups (control, intervention) with one outcome as yes/no(nominal) measure at two different times (before and after). What test?

I would not post this question if I haven't exhausted researching this very simple question. I have two groups. (intervention) and (control). We measured an outcome variable (let's call it X) as yes ...
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1answer
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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 ...
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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: ...
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22 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 ...
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58 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 ...
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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 ...
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1answer
24 views

Is it appropriate to use paired samples test for different days of the week?

Say we have a dataset of visitors to a mall: ...
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1answer
13 views

Paired or unpaired non-parametric 2 sample test?

I've got a relative simple question. I'm doing an imaging study with a phantom. I've run the same phantom through the MRI scanner 5 times, each time running the same scan twice and only varying one ...
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What analysis to use for ABA study design with repeated measures

I have a data set of ~50 subjects including demographic data, such as age, gender, employment, education, and the presence or absence of a health condition. Study Design looks like the following: ...
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2answers
61 views

Is a statistically significant difference within analytical uncertainty still valid?

The isotopic analyses of two tissues across 50 specimens showed a mean difference of 0.12 ‰. A Wilcoxon signed-rank test for paired samples indicated this to be statistically significant (Z: -2.515, P ...
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1answer
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Comparing two discrete paired datasets

The problem: I am studying the estimated number of cases of malaria in regions of the world and found that both the WHO and IHME have their own estimates. I want to find if the difference between the ...
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1answer
51 views

Can matched samples be analysed using regression?

Is it possible to use linear regression to compare matched samples in an observational study? In order to try to eliminate confounding factors, two groups were matched on a number of background ...
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Paired comparison of multiple variables, how/whether to adjust for multiplicity

I would like to ask for advice about which statistical test to use. I want to compare the control left and the treated right knees of the same 10 patients (n=10 per group, paired comparison). I did ...
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1answer
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Paired test or two-sample t-test?

I am looking at whether there is a difference in the extent of emotional tone in student essays on two exams - one at T1 and ...
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Linear model equivalents of classic within subject tests

I'm trying to build a broader understanding of linear models in the context of A/B testing. The situations I'm usually dealing with involve categorical within subject factors and testing if they have ...
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1answer
20 views

Which statistical test should I use? Change in number of intakes at several animal control facilities in a county

There are nine animal control centers in a large county. There's a database of intakes for several years. That dataset includes owner surrendered dogs. An extremely high percentage of those dogs are ...
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2answers
63 views

Sensibility and specificity with inconclusive cases (non binary problem)

I need to compare the diagnosis of two methods vs a gold standard (all is paired data). The results are categorical variables classified as positive, negative and inconclusive. How do you deal with ...
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Compare ratings of players over different leagues?

I want to compare ratings of players from different leagues and predict rating of player in a league he/she didn't participate in. Rating of a player is estimated within a league where he was playing. ...
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Paired t-test on large sample that *should* be normal, but isn't (or Wilcoxon Signed Rank Test)?

A dataset contains the number of fast food restaurants per thousand people for each county in the USA, for two different years (five years apart). 3,143 rows. None of the following are normally ...
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1answer
18 views

Why can the null and alternate hypotheses of McNemar's test be written in terms of dependance/independance of tests?

Consider a study to examine whether food frequency questionnaires and three-day food diaries are equally likely to label a women as consuming less than the RDA of calcium. Because calcium intake can ...
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24 views

Correcting for multiple paired comparisons within a large number of subjects

As the first step in an analysis of a large dataset, I am looking to identify a subset of subjects that are shown to have a significant response to at least one event condition. This involves looking ...
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1answer
29 views

Paired T-testing or ANOVA?

I have data of the structure below. im confused about using paired sample t-testing vs ANOVA. Paired T-tests make sense to me, but im worried; because there are 7 outcome measures, am i violating some ...
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1answer
33 views

Comparing experimental and control group consisting of two measures for each participant

I'm conducting an experimental study. For each group (treatment/control) I have measured the biometrics of both eyeballs (left/right) of each participant. Can I make a comparison between values of ...
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26 views

How to plot a 100 variables paired t test and correlation matrix

I have more than 100 variables from a biological data for which I have values for before and after surgery. I am doing two analysis: A paired t test for before and after measurements. A ...
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1answer
18 views

How to analyze clinical outcomes after propensity matching

Suppose I have two propensity matched groups whose covariates are balanced. How do I analyze clinical outcomes between the groups. I would be interested in overall survival, one year survival, and ...
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1answer
29 views

Using paired t-test or Sign test to compare two groups of correlated measures on the same subject?

I have conducted a survey where participants are shown 8 different advertisements: 4 of the ads attempt to evoke the feeling of guilt, 4 others attempt to evoke the feeling of shame. After seeing each ...
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Paired Comparisons and Ranked Lists

Here is a brief description of my experiment, to help you understand the data and question Individuals perform pairwise 2AFC (alternative forced choice) comparisons between two categories of items at ...
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1answer
19 views

One Way ANOVA or One Way ANOVA with repeated measure

I have LFS spanning 24 quarters, and I want to look at the effect of a policy on the sickness absence of a particular occupation. I want to use ANOVA to see if there is a statistically significant ...
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15 views

How, if ever, is quantile linear mixed model compatible with the signed rank test?

Paired Wilcoxon test evaluates median change rather than difference in medians. Quantile linear mixed model (defined for medians) evaluates change in the medians, rather than median change, as any ...
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1answer
19 views

Does mixed model of change evaluate mean change or change in means?

Paired t-test evaluates mean change. Mixed models evaluate change in means. How the two can be compatible? For balanced data it works - paired t-test = random intercept model = GLS with compound ...
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11 views

Which significance test should be used to compare models based on Monte Carlo (holdout) cross-validation?

I have created two machine learning models and want to run significance tests on the results of various metrics (sensitivity, specificity, Cohen's kappa etc.) to see if there's any statistically ...
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5 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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23 views

Coding data for regression on unordered pairs

I want to fit a regression on "unordered paired data", but I'm uncertain on how to code it. What I mean by paired data is the following: The model looks like this: $$o_i \sim \text{Binom}(1,p)\\ f(...
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21 views

Calculating Standard Deviation of difference of means from summary statistics

To conduct a paired T-test, I need to know the standard deviation of the difference between two means. How can I find this out using summary statistics alone (the mean of the Kappa value for each ...
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16 views

What is an appropriate repeated-measures approach for statistically comparing results from two different methods?

I have a diffusion MRI dataset, with values of white matter tract volume and fractional anisotropy that were derived using tract masks generated from two different tractography software packages. I ...
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1answer
56 views

In a paired test, what constitutes a valid pair?

The title is my question, here is a little more information. I was checking off on an analysis done by someone else and they used a paired t-test on data from the same subject; however the difference ...
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16 views

ANOVA testing for User Activity on a website

Problem: I am trying to determine whether visitors on a web-site are more likely to perform a certain action (click a specific button in this case) if they view a specific section on the website. I ...
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2answers
88 views

Multi-variable logistic regression for paired data in SPSS?

I was hoping for some assistance regarding performing a multi-variable logistic regression for a matched data set. I am not formally trained as a statistician (biology trained with basic stats/SPSS ...
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1answer
50 views

How to control for within-subject covariate in a single-arm, mirror image study design?

I have a mirror image study which consists of one group of subjects, and they have a measure before and another measure after an intervention. Depiction: Single group: Measure#1 -> (Intervention) ->...
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1answer
45 views

Can a paired t-test be applied when there is no strict pairing but data come from same individual?

The question is if it is possible to apply a paired t-test in the following situation: Let's say we have conducted an experiment to measure how long does it take to perform a task under two different ...
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18 views

Paired T-Test Question

If you have two paired groups (group A and B) and want to determine the difference in the two means, you would use a t test for two related populations. However, what if you want to determine the % ...

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