Group differences broadly refer to statistics which quantify the differences between two or more subpopulations.

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Detecting heterogeneity in groups

This is a mockup of a dataset I am currently working on: ...
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Difference test between 2 groups where both groups contain depended and independent observations

Is there a statistical test to check the difference between groups (for example a paired sample proportion test), but where some of the observations of the two groups are dependent and some of the ...
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Mode of the difference of two beta distributions

Given two beta distributions $X \sim \beta(m_1, n_1)$ and $Y \sim \beta(m_2, n_2)$, how to compute the mode of the distribution of $Z = X - Y$?
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23 views

Test of significance of multiple proportions in two groups

I have a dataset of two genetically different cell types, "A" and "B", and each of them can have four different morphologies, let's say "spiky cell", "elongated cell", "round cell", "triangular cell". ...
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111 views

Plotting averages when there are missing values

I have count data for a number of subjects in different groups I would like to compare. The averages of the cumulative sums are shown in the figure below. As you can see the Red group has a spike at ...
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163 views

Visualizing large dataset with multiple subgroups

I have a large data frame in the following form (I apologize for this formatting): ...
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80 views

In a meta-analysis, how should one handle non-significant studies containing no raw data?

Let's say that I'm conducting a meta-analysis, looking at the performance of group A and group B with respect to a certain construct. Now, some of the studies that I'll come across will report that no ...
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17 views

Different group size average comparisons

I have 3800 stocks for which I calculate their return correlations. So I end up with a 3800 by 3800 matrix. Each stocks is related in some way to all the other 3799 stocks. For each stock, I create ...
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8 views

correlation between the same group

I'm doing a statistics paper in which I have to correlate the clinical diagnosis with the hystopathological one. So, basically I have one group of people with 2 different diagnosis: 1. clinical 2. ...
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40 views

Comparing different conditions on a binomial distribution

I have some data where I have tested a binomial random variable under 4 conditions. The null hypothesis is that they all have equal means, alternative hypothesis is that one or more means differ from ...
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10 views

How do I determine the significance of a difference in weighted averages from a Likert-type survey question?

I have multiple survey questions that give respondents 4 Likert-type options for a response to qualify their knowledge/skill in a particular area. I have calculated a weighted average (and divided by ...
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25 views

How to compare distributions of two groups where each group has multiple observations from a small group?

I have data on continuous measurements (length of time of a behaviour) from two groups of individuals which differ in their phenotype (phenotype A or B, the variable used to group them). Each group is ...
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27 views

Multivariate grouped data in R

I have a dataset of gambling expenditure, income, verbal reasoning test scores and gender. I tried two different methods for fitting a linear regression: ...
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35 views

What test of significance is best suited to compare concentrations, with only one sample of each population?

I have two large reservoirs of water with unknown concentrations of bacteria. I have only one sample of each reservoir: Sample of reservoir A: volume of the sample $=V_1$, number of bacteria in the ...
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45 views

Comparing two means: Same group, different variance (Welch's t-test?)

Intro: I have recently made a simulation program which simulates patients with Type 1 diabetes. In that context I am creating artifical patients. Let's denote three of these as $\text{p}_1$, ...
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1answer
62 views

Testing that two models from two different data sets are independent

I have two different sets $(n_1=47$, $n_2=23)$ obtained under different conditions. I fit two different functions $(\text{Fu}_1$, $\text{Fu}_2)$ in MATLAB. $\text{Fu}_1$ was fit using the first data ...
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2answers
73 views

Correlation and group difference with unequal sample sizes

My sample is 60 participants. At first, I did not expect to analyze the correlation, but the result is interesting, so I would like to. The 60 participants are 50 people who have good reading skill ...
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36 views

test of significance for comparing change between two groups

What test for significance is best to use to test the difference between the change of a categorical variable in a control group and the change in a pilot group? The variable had three categories ...
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96 views

Two-sample bootstrap?

I have two independent samples of observations. From each sample I produce a statistic. Let's denote these as $\theta_1$ and $\theta_2$. I'd like to test the hypothesis that $H_0: \Theta_1=\Theta_2$, ...
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91 views

How to separate groups using PCA?

I have two groups: A) controls: $25\times2000$, B) patients: $12\times2000$. Group A has ...
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51 views

Testing difference between two means. Skewed ( N1=21) vs Symmetric bell (N2=47). Wilcoxon rank sum test appropriate?

I need to test to compare the means of two samples, one with size 21 and the other with size 47. Histograms show Sample 1 is skewed to the right while Sample 2 has a bell symmetrical shape. ...
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77 views

Chi-squared test when two vectors have different lengths

I want to compare two groups (vectors) having different lengths to see if their distributions differ considerably. However, when I use chisq.test, I get an error ...
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17 views

How to assess variance in whole genome biological data?

I am a biologist by training and have started a project assessing “variability” using microarray data. The microarray takes a measurement (expression level) of ~20,000 genes for each sample, and I ...
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60 views

test for comparing means of two time series [duplicate]

I wonder if there is a test for comparing means of two different time series (both measured at the same person or two different persons)? Would be very glad if someone can help me!
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35 views

Comparison of means for individual vs consensus

I have a question regarding how to evaluate agreement between an individual's rating, and that of a group of people (of which the individual was a part). The group score was achieved through consensus ...
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132 views

Analysing significance in grouped variables

I have imputed a dataset which has 20 observations. Participants were asked to rate the importance of 13 variables under a certain circumstance, from 0 to 25. I imputed this using ...
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26 views

Comparing groups of different sizes in social network analysis

I've got social network data for three groups of chimpanzees and I'm looking to do some basic analysis across and between groups. Does anyone by any chance know how to compare social network data ...
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Assessing group differences on multiple outcomes

I have one independent variable with two levels: Gender (Male and Female), and dependent variables will be composed of three test scores: Impulsivity, Assertiveness, and Social Desirability. My ...
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205 views

Unequal sample sizes: When to call it quits

I'm peer reviewing an academic journal article and the authors wrote the following as justification for not reporting any inferential statistics (I deidentified the nature of the two groups): In ...
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56 views

How to calculate the 95% CI of the difference in population means?

Suppose I want to determine if treatment T affects parameter X, and by how much. I have a sample of subjects that received no treatment, and can calculate mean X(control) with associated variability. ...
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46 views

Correlation between different groups (based on an ordinal variable) and a Likert variable

I have a table with responses of a survey. Now I want to test the statistical significance between 3 groups of respondents. There are two columns I'm interested in. The first is an ordinal variable ...
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48 views

What test of significance should I use to analyse visits to a clinic by various groups?

Apologies for the noob question. After a day on Google and Wikipedia I still can't quite work out what to do. So here I am. A small private healthcare clinic in the UK has asked me to look at their ...
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22 views

Repeat normality check after modifying group cut-off?

I have a set of data which consists of one independent variable (2 groups) and one dependent variable. I successfully checked for normality (each group separately) and conducted a t-test. Now I want ...
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26 views

Compare regressions among more than 2 groups

I would like to know if there is a way to compare the relationship between a factor (length) and a response variable (lipid content) among multiple groups? I have given up on ANCOVA, as length is ...
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37 views

How to test difference between two groups of data in one line

Usually, we can test difference of two groups of data by adding the dummy variable. But my question is, if these two groups of data in the same line, but they concentrate at the different part of this ...
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Comparing groups with multiple related variables

I have four groups with six subjects in each group. For each subject I have measured their mean blood pressure every minute for 3 hours. This means that I have 180 variables. The first 60 minutes ...
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Testing hypothesis for multiple groups in two settings

I am testing six groups on six different websites that fall under two categories (responsive websites and mobile websites). Each group contains 10 participants. One group rate one site in one ...
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34 views

Which statistical test(s) do I use? (Groups, time series)

10 species were sampled over 5 time periods (put simply, growth is the measured variable). Now I'd like to find out: Do the measured values significantly differ between species within each time ...
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Compare variance and point statistics in a 3 way group

I need some help on this analysis. I have 3 groups of individuals, different the level and kind of physical activity. For each individual I have the heart rate, taken every minute for ~24h. (each ...
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62 views

How can I use likelihoods to compare these three groups? Should I want to do this?

EDIT: Perhaps I should also note that my initial attempt at analyzing this data used a hierarchical model in rJAGS sampling the means from uniform distributions and variances from gamma distributions ...
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80 views

How to compare differences in the mean when the data isn't normal

I have two sets of mean data that I have done a Kolmogorov-Smirnov test on. The tests came back showing that one data set was normal, but the other was not. The two data sets are independent of each ...
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49 views

Comparing the mean of two non-random sub-groups

Students are assigned to group A or B based on two aspects: a grade from an exam and an evaluation of their teacher. Students with both a high grade and a positive evaluation get into group A, other ...
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Differentially “expressed” features

When any person gets a dataset of counts for two groups (metagenomics or digital gene expression), the first thing they do is to go and find features that differ significantly between the two groups, ...
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69 views

Robust test for time series count data

I'm going to analyse suicide rates for a time series, and I'd like to use robust tests, but I don't know which would be a good one. My purpose is to compare the variation of the suicide rates through ...
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83 views

Comparing population proportions vs hypothesis testing

The author of a famous online course takes a problem where 642 of 1000 polled men and 591 of 1000 polled women responded yes. The question is if men are more likely to agree or not, using 95% ...
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96 views

significant differences between groups in gender

I have a cell array containing the gender e.g. GENDER = {'Male';'Female';'Male';'Male';'Male';'Female';'Female';'Female';'Male';'Male'}; and another array ...
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33 views

Comparing two cumulative distributions

For our study, we're gathering internet pages in our database, selected using an alerting system and dividing them in some categories. Periodically, we want to compute the "social sharing level" of ...
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45 views

Estimating number of RNA-seq reads needed to detect differential expression

So I've spoken with two professors about this and I'm still confused. Maybe I need to see it in writing (I'm a visual learner). This is an experiment with Drosophila (fruit flies). Currently, our ...
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175 views

Meaning of standard deviation of the mean difference

I'm trying to understand the meaning of stating the standard deviation (SD) of the mean difference (MD) [or otherwise called the absolute mean difference]. This is for a paper I'm writing up where ...
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Official name for “symmetric percent difference” function (x-y)/max(x,y)

I frequently use this formula to compare two positive numbers $x$ and $y$ to see if they are "more different" than some threshold: $$ x-y \over \max(x,y) $$ It is nice because it is symmetric and ...