Statistical Analysis Stack Exchange
Statistical Analysis Stack Exchange

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.

Paired data arise when an experimental or observational study design deliberately samples two units as a dyad to form a basis of comparison. Typically these units are highly correlated and thus warrant the use of statistical methods for correlated data. Examples of paired designs include twin studies, case-control studies with 1:1 matching of cases to controls, split-plot experiments, and pre-post tests. Examples of conditional likelihood based statistics include a paired t-test, conditional logistic regression, and McNemar's test.

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t-test for partially paired and partially unpaired data

An investigator wishes to produce a combined analysis of several datasets. In some datasets there are paired observations for treatment A and B. In others there are unpaired A and/or B data. I am looking for a reference for an adaptation of the…
Frank Harrell
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What is the difference between the Wilcoxon' sRank Sum Test and the Wilcoxon's Signed Rank Test?

I was wondering what the theoretical difference is between the Wilcoxon Rank-Sum Test and the Wilcoxon Signed-Rank Test using paired observations. I know that the Wilcoxon Rank-Sum Test allows for a different amount of observations in two different…
Snowflake
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Paired versus unpaired t-test

Suppose I have 20 mice. I pair the mice in some way, so that I get 10 pairs. For the purpose of this question, it could be a random pairing, OR it could be a sensible pairing, like trying to pair mice from the same litter, of the same sex, with…
David Epstein
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How to display error bars for cross-over (paired) experiments

The following scenario has become the Most-FAQ in the trio of investigator (I), reviewer/editor (R, not related to CRAN) and me (M) as plot creator. We can assume that (R) is the typical medical big boss reviewer, who only knows that each plot must…
Dieter Menne
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Difference in Means vs. Mean Difference

When studying two independent samples means, we are told we are looking at the "difference of two means". This means we take the mean from population 1 ($\bar y_1$) and subtract from it the mean from population 2 ($\bar y_2$). So, our "difference of…
user84756
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Compare two survival curves for paired data

I want to compare two different methods for detecting status change in a survival analysis. A group of subjects is being followed for a longer period (many years), and two examination methods have been used to examine whether a status change has…
Pelle
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In what situation would Wilcoxon's Signed-Rank Test be preferable to either t-Test or Sign Test?

After some discussion (below), I now have a clearer picture of a focused question, so here is a revised question, though some of the comments might now seem unconnected with the original question. It seems that t-tests converge quickly for symmetric…
justme
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How can a t-test be statistically significant if the mean difference is almost 0?

I am trying to compare data from 2 populations to tell if the difference between the treatments is statistically significant. The data sets appear to be normally distributed with very little difference between the two sets. The average difference is…
Kscicc26
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Choice of path weights in SEM conceptual models for identical & fraternal twins using openMx

I am reviewing the R package OpenMx for a genetic epidemiology analysis in order to learn how to specify and fit SEM models. I am new to this so bear with me. I am following the example on page 59 of the OpenMx User Guide. Here they draw the…
AdamO
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How to choose between sign test and Wilcoxon signed-rank test?

I am trying to pick one from these two tests to analyze paired data. Does anyone know any rules of thumb about which one to pick in general?
Sheldon
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What's a good way of graphically representing a very large number of paired datapoints?

In my field the usual way to plot paired data is as a series of thin sloping line segments, overlaying it with the median and CI of the median for the two groups: However, this sort of plot becomes much harder to read as the number of datapoints…
ali_m
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Paired t-test for binary data

I have one sample with n=170 and two binary variables (A,B) that can take as a value 1 or 0, where 1 counts as a success and 0 counts as a failure. What I want to know is whether the means of these two variables are equal. To find this out I…
Martin
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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 variance. If $S^2_1$ and $S^2_2$ are the sample…
Denis Cousineau
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Which model should I use for Cox proportional hazards with paired data?

I am hoping someone can help me with which model (frailty, strata or cluster) I should use for my data. I have paired data so I need to take that into account when modelling the Cox PH and am unsure which model will give me a more accurate…
Emma
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How to fit Bradley–Terry–Luce model in R, without complicated formula?

The Bradley–Terry–Luce(BTL) model states that $p_{ji} = logit^{-1}(\delta_j - \delta_i)$, where $p_{ij}$ is the probability that object $j$ is judged to be "better", heavier, etc, than object $i$, and $\delta_i$, and $\delta_j$ are parameters. This…
Silverfish
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