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

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identify different points

I have a large scatterplot, with about 100,000 (x,y) points. The x coordinate is the set of numbers from (1 to ~100,000) - in other words, no 2 points have the same x-coordinate. The y is mostly ...
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29 views

Averaging z scores when doing a “group by”

I have a dataset where each row is an hourly measurement of certain fields (columns). For each column I then add another column that is its respective z score relative to the entire population. If I ...
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9 views

Combining Standard deviation 3 groups

Is this the correct formula for combining the standard deviations of 3 groups? $$ \sigma = \sqrt{\frac{n_1\sigma_1^2 + n_2 \sigma_2^2+ n_3 \sigma_3^2+ n_1(\mu_1-\mu)^2 ...
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44 views

Is two-factor ANOVA without replication appropriate for my application?

I want to analyze results from a computer simulation in which I will vary two factors: (1) fan location, and (2) fan flow rate. After the simulation, I will query the results for gas concentrations ...
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52 views

Data transformation and confidence intervals for mean difference

I have a between-group independent variable with two level (A and B) and a dependent variable Y that I transformed in order to normalize the distribution of the residual. I used a Box Cox ...
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26 views

difference in pre and post populations

I'm looking at the difference in demographics of people with a disease pre-outbreak and post-outbreak (e.g. age, sex, location etc). I know how to use $t$ tests and $\chi^{2}$-tests for comparison ...
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84 views

Test whether time of maximum differs across two groups

Suppose I have 10 repeated measurements of a quantitative variable $X$ of the individuals within two groups (let's call them A and B). For each group, I have the estimated means of variable $X$ at the ...
6
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1answer
71 views

ordinal regression or Spearman correlation?

I am conducting research investigating two different groups of women: one group of Short-Stature Women (SSW) and another with Non-Short Women (NSW). We have the hypothesis that SSW has an inaccurate ...
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19 views

Longitudinal Monitoring: How to test if a parameter changes before the gold standard

I have some data that I am really uncertain how to analyse. Each subject who all begin as healthy/normal will undergo a series of imaging examinations during therapy: scan 1 (baseline), scan 2, scan ...
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23 views

Change in Proportion - Multiple Periods

So I have data consisting of a binomial variable observed in multiple time periods and I want to use a statistical test to determine the existence of a change over time. So here's how it looks: ...
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17 views

Significant difference

I have two answer pools for the same survey. I want to compare these answers that came from 2 different groups. Or I want to somehow see if these two groups share the same ideas about asked ...
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34 views

Confused about the basic maths in Incremental/Uplift modelling

I have recently gotten to study Incremental modelling, which is used in Marketing to study the incremental impact of a certain action on a treatment group against a control group. However, I am very ...
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2answers
87 views

Why test for both correlation and groups differences using the same variable?

A paper asks four research questions which deal with the measurement of latent trait x, a continuous variable which is acquired through learning or practice, and the speed with which the knowledge or ...
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1answer
20 views

Accounting for groups in GzLM Poisson regression

I am currently trying to perform a regression on data with one predictor and one covariate. The hypothesis I am trying to test is whether the incidence of pores (a hole through a cell) increases when ...
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1answer
29 views

Contradictive results of correlation and intergroup comparisons

I got strange results in spss and I don't know how to explain them statistically. I made correlations between: 1) personality and emotional inteligence (EI) 2) personality and emotional competence ...
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45 views

First-differences vs. pooled OLS

Two-period panel regression model: $Y_{it}=\beta_0\delta_{t2} + \beta_1X_{it} +\alpha_i + \epsilon_{it}$ where $t=1, 2$ $i=1,...,n$ indexes the cross sectional units drawn via random sampling. ...
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1answer
52 views

Should I use ANOVA or MANOVA?

I have data on two groups...I have one independent variable (times 1, 2, and 3) and a dependent variable fitness score (which includes score of a person's heart rate in five stages of the test, ...
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1answer
31 views

Grouping cases on certain criterion

You experts have been helpful so many times that I read others' threads, but this time I have to ask a new question. Long story short I need to group all my cases into 4 categories. Could someone ...
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38 views

Power analysis for post hoc test of ANOVA with many groups

In both G*Power and the R pwr package, estimated sample size required per group decreases as the number of groups increase. This seems somewhat counter-intuitive. For a toy example, assume that I ...
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33 views

Using similarity matrix to measure diversity of a group

I wish to measure the "diversity" of a group of objects. Right now I'm using Euclidean distance to compute the similarity matrix between all the objects in the group. I'm searching for a measure of ...
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1answer
18 views

How to compare the magnitude of a response among two groups?

I performed generalized linear mixed models to test the effects of a treatment on two different groups (I performed a model for each group). Now I would like to test which of the groups is most ...
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2answers
92 views

Using multiple linear regression to distinguish two datasets

Consider two datasets, a study dataset with $n$ points and a control dataset with $n_c$ points, with $n$ I would like to evaluate the hypothesis that the study dataset has a different Y (in average ...
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2answers
62 views

Determine if a % Change occurred

I'm trying to figure out if a change to a website that occurred on a specific date increased page views on that site by 5%. I have page view data for a month before the change and several weeks after. ...
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41 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 ...
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1answer
17 views

Are slopes of calibration experiment different?

I'm running a calibration experiment for an instrument that measures soil moisture content. I have 6 buckets filled with different soils that I weigh daily and at the same time take a measurement with ...
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60 views

How does my questionnaire analysis plan sound?

I will soon have the results of a questionnaire that I have carried out, and I have made a plan on how I will analyse the data. I was hoping that someone could comment on my plan to advise me. About ...
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44 views

Best ARIMA Model

What ARIMA model would be the best fit for the data provided?: ...
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27 views

Detecting heterogeneity in groups

This is a mockup of a dataset I am currently working on: ...
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37 views

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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23 views

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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1answer
50 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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4answers
118 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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1answer
259 views

Visualizing large dataset with multiple subgroups

I have a large data frame in the following form (I apologize for this formatting): ...
7
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2answers
113 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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1answer
25 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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10 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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57 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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0answers
17 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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1answer
35 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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39 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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1answer
39 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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1answer
73 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
70 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
199 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 ...
0
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1answer
105 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 ...
3
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0answers
104 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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1answer
112 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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1answer
76 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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1answer
212 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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25 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 ...