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Questions tagged [group-differences]

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

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3k views

Compare the statistical significance of the difference between two polynomial regressions in R

So first of all I did some research on this forum, and I know extremely similar questions have been asked but they usually haven't been answered properly or sometimes the answer are simply not ...
16k views

How to test whether subgroup mean differs from overall group that includes the subgroup?

How can I test whether the mean (e.g., blood pressure) of a subgroup (e.g., those who died) differs from the whole group (e.g., everyone who had the disease including those that died)? Clearly, the ...
19k views

Comparing two binary variables of unequal sizes

I measured a binary variable from two different populations, and now I'm trying to find out whether the different populations differ with regards to this variable. I could use a Chi-Square test, but ...
3k views

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 ...
47k 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 ...
2k views

How to test group differences when neither parametric nor nonparametric assumptions are met?

Consider following example. We asked 50 men and 50 women one question and they answered on 5 point likert scale (1 is completely disagree and 5 completely agree). Suppose that 50 men responded 20 ...
13k views

How can i calculate the 95% confidence interval of an effect size if I have the mean difference score, CI of that difference score

Mean difference: 3.7 CI(1.4-6.0) Cohen's d=0.4 how do i calculate the 95% CI of this effect size?
9k 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 ...
2k views

How to interpret Mann-Whitney's statistical significance if median is equal?

Testing the difference between the observations of two groups by using Mann-Whitney Test has given the following output (from minitab): ...
118 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 ...
2k views

What is effect size… and why is it even useful?

I have an introductory-graduate-level statistics background (assume I know mathematical statistics and probability at an undergraduate level (e.g., Wackerly et al., Ross' Probability), and have some ...
7k views

How to determine the cut-point of continuous predictor in survival analysis, optimal or median cut-point?

everyone! I want to do overall Recurrence-free survial analysis for one continuous predictor with Kaplan-Meier method, but the determination of the cut-point for groups really confused me. Most ...
188 views

Investigating differences between populations

Say we have a sample from two populations: A and B. Let's assume these populations are made of individuals and we choose to ...
593 views

Overview of concepts of the methods that this Single-Cell Differential Expression (SCDE) tool uses?

I'm unsure about how this tool works, but as I understand it, it tries to use Bayesian probability in order to differentiate the two different groups from each other as well as some other methods. ...
1k views

Should I re-center variables when looking at moderator effect in men and women separately?

I want to see if an interaction variable in a multiple regression is significant for the whole sample, and then just for men and just for women. When I created the interaction variable for the whole ...
581 views

Difference between normality of residuals vs normality in each group.

I've been searching on the internet and books for quite a long time now and have come to the conclusion that normality of the residuals (each values minus the mean of each group) is the same as ...
200 views

Claiming validity of a study's negative finding

For a disease that I am interested in, five or six published works of research have shown an association of changes in gene expression with presence of the disease. However, all these diagnostic ...
208 views

1k views

How to separate groups using PCA?

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

Comparison of two populations by analyzing the dependence of a single dependent variable on several independent ones

I am looking at two populations on which I have measured 4 independent variables ($X_1$, $X_2$, $X_3$, $X_4$) and one dependent variable ($Y$) along with each measurement or observation. I suspect ...
338 views

Comparing multiple mean scores using t-Test

Situation: Comparing mean scores of level of satisfaction across multiple institutions and overall. Let's say there are 50 institutions, all with different sample sizes. Level of satisfaction is ...
311 views

getting rid of the batch effects

I have a two data set one with $n=15$ another with $n=25$. Each set of data has around 90 variables. The data collected was experimental so when I try to combine my two datasets I see clear ...
42 views

Estimate group averages

If I have 100 numbers from two separate groups $X$ and $Y$. How can I manually estimate or derive an algorithm to automatically estimate $AVG(X)$ and $AVG(Y)$? I know all the numbers, but I don't ...
111 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 ...
I have four samples $x_1, x_2$ and $y_1, y_2$ with $n_{x1} \neq n_{x2} \neq n_{y1} \neq n_{y2}$. I calculated, using a Wilcoxon rank sum test, that $x_1$ is significantly different to $x_2$ and $y_1$...
A data set contains 5 columns: There are 16 people in the dataset(using subjectID to identify them). Each year, when these people were ages 11, 12, 13, 14, and 15, they provided us a score $y$. We ...