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

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How to calculate the average age of a subgroup

Just to confirm my findings to a group of data scientists... I have a data set with patients visits and among others the death age of deceased patients. If I then look up all diagnoses the patients ...
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17 views

Sample size for group comparison

I am collecting data from 3 different population groups (islands) and within each, comparing children from class 1 from 10-14 schools between two groups - those who completed kindergarten, those who ...
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78 views

Can the difference between the means of two groups lie outside the confidence interval for the difference?

I received this question from a colleague which left me with a desire to find out a bit more about it. If you have two groups A and B with means--for example, 7.9 and 5.8--is it possible that the ...
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24 views

Intuition behind fixed effects

Im trying to explain the intuition behind fixed effects to a group of people with no background in (formal) regression analysis. Explaining the intuition behind Diff-in-Diff estimation of the impact ...
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14 views

Testing if two population means are equal

In the situation where I have two estimated population means, and I want to see if they are equal, I compute $\frac{ \bar{y_1} - \bar{y_2} }{ se(\bar{y_1} - \bar{y_2}) }$ and compare to the ...
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49 views

Creating groups using two continuous variables without using median-splitting?

I have two continuous variables, one of individuals' retrospective childhood anxiety and another regarding their current level of anxiety. Research has demonstrated that during a snapshot of ...
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7 views

What are the conditions for Pooling Samples

I am trying to understand when it is ok to pool samples. The problem i have is that with more then two samples, it is possible that pairwise comparison of the samples could lead to the following ...
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1answer
27 views

Significance of differences between two scenarios

CAPTCHAs are used to distinguish legitimate human users from computerized programs that are trying to abuse online services. There is a way to bypass the security by relaying CAPTCHA challenges to ...
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13 views

Significance of effect on several variables

There is data about a supply chain model available. Below, you can see means of the calculated performance measures cycle time, return of investment, and service level for different forecast errors. ...
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41 views

Find whether one mean is very different from all others in multiple measurements

I have many data frames like the one reproduced below in R. I am trying to find cases where one group only is very different from the other groups (I have a variable number of groups for the different ...
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9 views

Comparing Frequency Distributions with non-categorical data

Rather than try and contrive things, I'll just give you the data as is. This similar to the ideas found here. I have two population from a control group and a disease infected group. I want to ...
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23 views

Comparing differences between overlapping groups

I am trying to analyse the differences between people who vote in the European Parliament (EP) elections and people who vote in national elections, based on the EES dataset (http://eeshomepage.net/). ...
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31 views

Difference in proportion: Pre-post intervention-control study design

I am conducting a meta-analysis where I want to compare the proportion of samples pre- vs post- intervention. To do this, I have been calculating the difference in proportion (Post - Pre) as the ...
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9 views

Test for participant subgroups in gradual means shift

In an experiment with 44 participants I have measured the response time for a set of stimuli, where the response could be a or b. The means of the two responses do not differ significantly (783.3 vs ...
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25 views

How to compare repeated measurements among groups with non-normal data?

I want to investigate differences in two variables among 3 groups. The variables are "% of time active" and "latency to exit a cage", and each group corresponds to a different context (the focal ...
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6 views

What type of within-subjects design should I use? Error-rates, Distances

I know I need to use a within-subjects design for this, but I can't figure out what type of design to use. I am an amateur at statistics and haven't taken a statistics course in years. I will try to ...
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34 views

What kind of chart to use when comparing two sets of data, each with an X and Y?

So I did a survey for a class at school, and I am looking for a correlation between how often people read the news, and their opinion on a certain current event. People rated their up-to-dateness on ...
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34 views

Efficient weighted 1D Clustering (Grouping)

I'm dealing with the simple problem of grouping a set of 1-dimensional data (1 feature) according to its distribution in the 1-D space. I know exactly the number of groups I will like to get. So for ...
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61 views

McNemar or chi-square - test for group differences paired and unpaired data

I understand that the difference between a chi-square test of homogeneity and the McNemar test is that the chi square is used for unpaired data and the McNemar is used for paire data. Here's my ...
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41 views

Performing significant difference tests in endline evaluation

we have conducted an endline survey and now comparing the result with baseline survey. I am interested to find significant difference between baseline and endline. One of sample questions is given ...
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1answer
40 views

Comparing sets of noisy discontinuous curves / histograms

I have a dataset composed of measurements of signal intensity along a line; visually they look roughly like the right half of this: Each sample is a discontinuous "curve" composed of roughly 600 ...
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90 views

Test of between groups difference in r-squared value in linear regression

Running a linear regression with one continuous IV (sleep) and one categorical IV (gender). Have run a split-file analysis and there appears to be a difference between genders in r-squared. How would ...
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7 views

Calculate standard deviation bitween 2 group of numbers

i'm trying to figure the right way to do this. senario : i have 2 groups of number that represent seconds(if it's matter). Group 1 : 1 , 2 , 3 , 4 ground 2: 1.1 , 2.3 , 3.1 , 4,1 i need to know what ...
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32 views

What do I use to describe the difference between two groups in terms of found latent variables

I need to describe what the difference between two groups (patients and normal controls) consists of in terms of latent variables that I can describe within each group. For instance, given this PCA ...
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96 views

Counterintuitive result when comparing two groups of time series

I have two groups of time series and I am testing the hypothesis that the groups can be distinguished in some way. Each time series is measurements of an individual’s pupil size as they listen to an ...
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1answer
76 views

Distribution of Sample Means Compared to Population Mean

Assumptions I have a population (n=5000) and I know everything about it (all point values, mean, standard deviation, etc.) From this, I will sample 1000 items. I can calculate the mean of the sample ...
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30 views

Longitudinal design: how to take into account baseline measures

I have a (small) data set of 15 subjects randomly assigned to one of two groups. All subjects were measured at 7 time points. Ideally, I would like to answer if the groups differ at certain time ...
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31 views

1-way and 2-way ANOVA giving wildly different results

I'm hoping someone can help me understand this. I'm using sigmastat 10. My data consists of multiple outcomes (2 continuous and 2 count) belonging to 3 groups (test/sham/naive). If I perform a 1-way ...
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64 views

Comparison of average variances between groups of different size

I have 3 groups, split by highest degree of education. For each individual in a group, i calculate the variance of her income in a five year window. Let's for simplicity assume that i only do this ...
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137 views

How to compare count of two groups?

I have a two groups of data - 1/ All data and 2/ Selected_season, which is only some subgroup of all data. I want to find out: a/ if proportion of BM, HB, etc. groups is the same in All data and ...
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21 views

Difference between two vectors of unequal size

I have a predictive model function mPred and two different input variables matrices of the same size (nxm), iM1 and ...
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29 views

Determine how much and why a sample differs from its population

I'd like to be able to determine a) how much and b) why a non-random sample “differs” from the population (there's probably a better word than “differs”; I was tempted to use “does not represent” but ...
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36 views

Running many $t$-tests to find the most significant way to divide a dataset

I apologize for my stats illiteracy in advance–I'm not a stats guru by any stretch, but am trying to learn. To start, I'll just introduce what my data set looks like, then what I'd like to ...
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37 views

Confidence bands for difference of time series

Assume that I have two time series $Y_{1t}$ and $Y_{2t}$ that are sampled at the same frequency. Is there a way to quantify the uncertainty in their difference $Y_{1t} - Y_{2t}$? That is, can we get ...
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29 views

How to test for a home bias in a data set?

I'm trying to think how I can test a data set I have, for transactions between buyers and sellers, for a home bias. My hypothesis is that buyers would rather buy from a merchant from their home ...
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43 views

Wilcoxon rank sum test for significant differences between two time points

I have data like so …(Col1:Companyname Col2:Data at timepointA; Col3:replicate Data at timepointA; Col4:Data at timepointB; Col5:replicate Data at time point B ...
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108 views

Multi-group SEM with a categorical outcome (using lavaan)

I'd like to ask the SO community for some help in regard to the interpretation of a structural equation model with three groups, featuring a categorical outcome. I have found a lot of sources treating ...
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42 views

How to properly group data for analysis

I am wondering what the most common way to handle data is wherein a participant belongs to multiple groups. For example, if you're wanting to run linear regression and look at how specific diet-type ...
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1answer
48 views

comparing a variable (that is repeatedly measured) between groups in R

I have a rather simple question (I hope) but for some reason I can't find the right/ a working answer anywhere on the web. For my research I have measured mood on a scale 1-10, 6 times a day for 5 ...
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2answers
72 views

Significant difference and correlations

Is it true that when there's no significant difference between groups then there will be correlations between groups? My situation is as follows: I have a sample that was measured using two ...
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1answer
42 views

How can I make clusters with highly right skewed data?

My histogram of expected income is as below. As you can see, income is highly right skewed. I want to divide individuals with regard to income - for example into Low, Middle, and High, and then I ...
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52 views

identify different points [closed]

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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83 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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17 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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70 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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1answer
345 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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44 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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1answer
88 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
166 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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25 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 ...