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

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12 views

Simulation study of type I error rate in nonlinear mixed effects model => anti-conservatism or coding error?

I've run a simulation study in order to estimate type I error rate of the test of group effect in a nonlinear mixed effects model, using nlmer from lme4 package. The results show there is 8-10 % ...
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18 views

Measure how different are two groups in their answering on 25 ordinal variables

The research context: I'm interested in usage frequency of special interest websites and its predictors. I asked individuals (n=1000) for the usage of 25 different websites in 25 items in a survey ...
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66 views

How to detect different social groups in a small questionnaire dataset?

I work with a very small questionnaire dataset, in which perception of 10 respondents to the size of, say, an unseen population is quantified: The population is divided into eight sub-populations, and ...
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2 views

Separate-Sample versus Pooled-Sample Estimation of Interactive Effects

I have a question regards pros and cons for Separate-Sample versus Pooled-Sample Estimation of Interactive Effects, when alayzing group differences. For instance, I am interested in the effect of a ...
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22 views

Test for group differences in a piecewise OLS

I have a piecewise regression and need to test for group differences. I want to test whether the two groups (a categorical predictor) differ with respect to a continuous, independent variable's (IV) ...
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19 views

compare groups taking into account confounding factors

I have data from human participants in a study and I am using MATLAB to analyse it. The participants are divided in 4 groups according to their disease severity. The demographic characteristics of the ...
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1answer
26 views

Difference between regression between groups vs across all subjects (continuum)?

I'd like to understand this better in terms of drawbacks and suitability. For example, if my data includes investigating differences between 2 patient groups and a control group (3 groups in total), ...
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8 views

Testing groups with categorical observable for significant difference

I am looking for a suitable statistical procedure to find groups of variables that are not statistically significantly between them when I have several dependent variables. I have a table containing N ...
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7 views

Which variables characterizes the separation of speakers into two known groups

I have 40 patients for which 12 summary measures have been computed. Some of the measures are somewhat correlated in the data, but measure quantitatively different things, so I would like to keep ...
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1answer
60 views

Linear trend for correlations

I am evaluating three independent samples (1-3). For each sample I have calculated a correlation of variables A and B. I am now interested if there is a linear trend in the development of the ...
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29 views

Two groups, 29 Likert scale questions - differences between the groups?

I've two groups of individuals, Group A (13) and Group B (30). Both groups got the same series of 29 questions that can be asked as "unimportant - slightly important - moderately important - very ...
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1answer
25 views

test for difference between two differences (proportions)

I have 4 independent samples. Two groups A and B measured on time1 and two groups A and B measured on time2. For every group I calculate a proportion. I would like to compare the difference between ...
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44 views

Comparison between groups with one group normally distributed, and the other skewed

I want to compare continuous numerical variables between two groups. Sample size is small (27 for one group and 43 for the other). I use Shapiro-Wilk test to check for normality of distribution of ...
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31 views

Comparison of ratios between multiple groups

I need to perform statistical analysis whether there is any difference in the usage of each gene version between disease groups. I have 3 groups, in each group there is a different no. of patients. ...
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1answer
19 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. ...
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31 views

Independence between sibling groups?

I am a novice at statistics and I would sincerely appreciate your help with my question: I am working with a control group and 2 sibling groups and have a mixed design (i.e., one withing group ...
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30 views

Okay to use oneway ANOVA to compare these 3 group proportions from aggregated dataset?

My situation: I am assessing outcomes of a university course redesign. One of the goals of the redesign project was to increase successful course completion, as measured by a decrease in the course ...
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1answer
32 views

What is the relationship between differential analysis and hierarchial clustering?

I'm currently in an internship for R bioinformatics, where I'm writing software for single-cell RNA sequencing analysis. We're looking for differentially expressed genes between groups, but I don't ...
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27 views

Figuring out which test to use

It's been a while since I've taken a stat's class and I came across a problem I need to solve. I was hoping someone could point me in the right direction. I know a question similar to this has ...
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1answer
22 views

How to quantify whether the difference between two groups is relevant?

I'm sorry that I am not at all an expert in statistics, so my question may sound vague, or very easy. I have a group of people that I divide into two categories, $A$ and $B$, depending on some ...
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1answer
29 views

Why does randomising the order of measurements remove time as a confounding variable?

Say we're interested in the difference in x between Group1 and Group2. We might measure 50 samples from Group1 then 50 samples from Group2. If the accuracy or precision of our measurements change over ...
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20 views

Generating predicted mean values and CIs across different groups in lme4

I’ve run a mixed-effects model with crossed random effects in glmer and ultimately want to show a bar graph depicting mean predicted values (and associated confidence intervals) across years within ...
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1answer
42 views

How to quantify the similarity/difference between groups of selected features?

Since I have a imbalanced data to deal with, I randomly down-sample the negative data to reach balanced data for following feature selection and classification. To test feature's robustness to ...
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30 views

Measure for comparing serial measurements of multiple variables in treatment vs control group?

Can anyone suggest whether I am going about the statistics in an appropriate way? I have two groups of populations which have similar characteristics. In each member of both groups, serial ...
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33 views

When/how should I bucket/recode/group certain categorical levels in an “others” level?

Imagine I have a dataset with a categorical variable with many levels, and I want to use this dataset for binary (positive/negative) supervised learning. In this categorical variable certain levels ...
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1answer
119 views

Comparing failure rates between 2 products with different number of deployed equipment

I have the following scenario, which I am trying to better understand. There are 2 different brands or groups of devices performing the same functionality as such: - Product/Brand 1 has 4,323 devices ...
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36 views

Pretest-posttest comparing two treatment modalities

I am not a mathematician, and have not studied statistics in 8 years. Medically trained conducting experiment for University, sorry for my ignorance. I am using an identical pretest / posttest, ...
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42 views

Difference between treatments with binary outcome & sample size estimation - Stata

I have 20 binary outcome variables that I want to test for association with a nominal 'treatment' variable with 6 categories (a,b,c,d,e,f). For the outcome that is significantly associated with ...
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59 views

ANOVA not significant but t-test significant

I have survey responses from people from 10 countries (sample range from 10 to 71 response per country) and I am trying to see if there are significant differences between the people of each country ...
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7 views

Using interaction terms to exclude sample members who do not meet certain conditions?

I believe this might be a specific application of the non-compliance problem in experimental design and estimating treatment effects, but I could be wrong. I want to model the impact of certain ...
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1answer
34 views

Is difference in proportions due to sample size?

I am currently working for a project team that is trying to reduce the number of defective parts produced in a factory. Without going into too much detail, the plant has a safety procedure where they ...
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40 views

Normalize data with kurtosis > 1 for one group

I want to model my variable using mixed linear modeling, but the problem is that target variable has a very high kurtosis for one group. The distribution is totally normal for other group. ...
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18 views

Comparing differences in pairs of ratings using a bootstrapping like approach

I'm pretty new to bootstrapping like approaches. So I do apologize for any inconvenience. I have two independent samples, snow (n=120) and nonsnow (n=608), consisting of pairs of ratings on a ...
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36 views

Power calculation for non-significant pilot study?

I have performed a pilot study comparing the means of two groups and I've yielded non-significant results. I wish to determine whether increasing the sample size would have produced a significant ...
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52 views

Strategy for geometric die guessing game

The first day of statistics class, we played a betting game to visualize the basics of probability distributions. It worked like this: The teacher begins by rolling a die repeatedly until the number ...
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61 views

At what point do significantly different groups start to differ?

I have two groups: a control group (N = 91), and a treatment group (N = 54). I did a t-test in SPSS that suggests that there are significant differences between the two groups in terms of the variable ...
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16 views

Find significantly different element

I have following data and want to know is there really significant difference between those five objects: I have 5 objects and 3 different tests and their results like this. So this is very few rows ...
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1answer
84 views

What test(s) should I use to compare 2, non-normally distributed populations with unequal variances? (IV is 2 categories; DV is ordinal)

I'm a bit stumped as to what test(s) is/are most appropriate for the following scenario. I found a couple of similar questions but wasn't sure if the answers applied. For a report I am working on for ...
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14 views

What's the best stats to use for pre/post data?

I have 107 participants and had them do 2 lessons. Before lesson one, I asked 5 knowledge questions with true/false response for each. After the second lesson, I administered the same survey ...
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1answer
46 views

Testing if subpopulation group is different from population group

Say I have data about the distribution of age groups in a country: 0-10 y : 20% of pop (or 3,000,000 people out of 15,000,000 total) 10-20 y : 30% of pop etc. ...
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1answer
78 views

conditional difference between 2 uniform random variables. Surely Breiman can't be wrong?

I've already searched and don't find this particular case in XValidated. Statement: "Electricity is turned on uniform-randomly at a given time of day (in 24 hour window). Once it has been turned on, ...
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7 views

Moderation with the outcome variable

I'd like to know how one can do moderation in the following scenario: Randomized experiment for a group-level intervention. HLM has already shown impacts of the intervention on individuals. The ...
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1answer
39 views

Searching for signal in a somewhat noisy landscape

I'm trying to implement a system to identify regions of high signal content in the presence of a noisy landscape. By high signal content, I simply mean intensity values significantly above background ...
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1answer
550 views
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16 views

Iterative Differential Expression Analysis for Multiple Categories

I have a dataset which consists of one categorical variable and many numerical variables. This is how my data is formatted: ...
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1answer
78 views

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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1answer
32 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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2answers
127 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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51 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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25 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 ...