Questions tagged [group-differences]

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

436 questions
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Differences between groups

I am currently doing a research on effects of writing styles on the perception of reader. Currently I have the following 4 groups ...
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How to compare ranked data?

I have some questions about how to analyze ranked data. The data looks like this: 4 groups of people with HIV and 16 other groups of people living in the same village were asked to rank 12 ...
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Matching covariates between more than 2 groups

I have three groups that I would like to match on age and gender. They don't need to be matched one-to-one, I just need group differences p < .05 for both variables. I can find packages that will ...
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How to test whether two means of categorisation generate significantly different results

If I have the following contingency table in which Novel.Cat is a new means of classifying some thing. Ref.Cat is the gold ...
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What is the equation for combining standardized mean differences across multiple studies?

I am trying to come up with a combined/pooled standardized mean difference for meta-analysis of a dozen or so studies that have the same binary predictive groups and the same continuous outcome ...
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How to analyze differences of two groups with replicates?

I am trying to see if there are differences between two groups (background genetic mutants) and some values associated to them. Every group has 4 different gene types with two replicates each and its ...
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Difference between two groups of unequal age

This is probably a very simple question! I am trying to compare two groups on a balance evaluation, a normal group and one with a neuro deficit. However, these two groups are significantly different ...
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How to test for differences between two group means when the data is not normally distributed and the sample size is small?

I have a preliminary study with very small sample size (n=26), and I want to test for differences between males and females and similar things, so I have to divide the sample and make comparisons of ...
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Comparing the result of a study which has unequal group sizes

I have conducted two user studies and in my studies I didn't have control over the group sizes. In each study users were put in groups and they were asked to perform some group activities. Here is the ...
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Should false discovery be controlled at the data acquisition level, or should this be at the data interpretation level?

Should false discovery be controlled at the data acquisition level, or should this be at the data interpretation level? I have an experiment in which microarrays were used to quantify the expression ...
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Analysis of participant's results to see who is the most different

What I'm trying to do is analyse results for an experiment I have conducted. An example set of results is ...
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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 ...
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What is the most appropriate test for this situation?

I want to statistically test the mean difference of a continuous variable (let's call this variable 1) between four groups (nominal) in my sample. Variable 1 has a very skewed distribution. This test ...
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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 ...
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Difference in proportions but one of them is 0

What is the best way to test for difference of proportions when of them is 0% (or 100%) ? edit: I have two raters, who give a score of either 1 or 0. One of them gave a 0 in every single case. Now I ...
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Test effect of variable across sub-groups logistic regression

I have a logit model where I am predicting stunting (a binary indicator of malnutrition), and my two binary independent variables (improved.water and has.insurance) are both statistically significant: ...
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Estimating ratios of quantile means for sorted data

In studying the relationship between income and consumption, it is common to sort the observations by income and observe that high-income households have lower levels of consumption per dollar of ...
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How can I compare the effect of an pre-post intervention between two groups with multiple numeric dependent variables?

I have collected data from two groups (age 25-30, age 30+). In each group I have 10 patients. I performed several medical tests (i.e., R.B.C, Liver test, etc.) on the patients, before and after ...
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How can I compare cancer counts by race for 4 types of cancer

I have a set of cancer counts (incidence) for difference racial groups for 4 different types of cancer. I'd like to know if there is a difference in cancer incidence among the racial groups. So the ...
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Is it typical for group means of composite z-scores to have means with values of the same magnitude but opposite signs?

I developed a composite score by converting four items to z-scores, then I summed up the z-scores to form a composite measure. However, when I've calculated means to compare finding for two ...
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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 ...
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How to compare two groups on a measure of social skills that includes 5 subscales where each subscale is number correct out of 12?

I have two groups of participants. Each group contains 30 children (15 girls and 15 boys). The first group has been sampled from a population of children being raised under some kind of constitutional ...
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Testing for equality of variance in permutations (microarray analysis with bioconductor)

I have measured whole-genome gene expression in two groups of animals, n=6 in each group. My goal is to detect differentially expressed genes - pretty standard analysis. The typical thing to do, and ...
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What statistical measures are recommended for mixing of population samples?

I want to know what statistics should be used to measure the mixing of languages in cities in a country/state. I have samples from individuals and know the language they speak and the city they live ...
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How do I test to see if the demographic proportions between two unequally sized groups are statistically different?

Sample of 102 broken into two groups based on a factor of interest Group 1, $n=77$ Group 2, $n=25$ Trying to figure out how to test if the demographic (age, race/ethnicity, gender, education level,...
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How to find group differences with irregularly measured, nested, and missing data?

Background: I have a dataset, which consists of waterlevel measurements over time at different locations. However, the locations are irregularly measured in different years. Therefore my data consists ...
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Significance test for two mean differences? Like a t-test but for comparing differences

I'd like to find out if there is a statistical test that I could use to determine if a mean difference is significantly greater than another mean difference. To determine if one mean is different ...
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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 ...
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How to compare two non-randomly selected groups within a sample?

I am quite new to Statistics, so please do not flame me for such a simple question. I made a controlled experiment and successfully gathered the data. 41 persons participated. They made a ...
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Reducing the number of groups of data by joining them

I have one variable that attains a certain value (between 0 and 1), about 1000 observations and each belongs to one (and only one) of fifteen groups. Now I would like to reduce the number of groups to ...
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How to determine how many unique visitors should be in the control group

Let's say I want to perform an AB-Test with the following properties: We assign unique visitors to each group, not the requests (so each trial corresponds to a unique visitor as long as e.g. the ...
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How to symmetrically adjust data by removing certain value

Say I have a data set in the following format: {a:200, b: 100; c:400} The sum of a, b and c equals 700. Now, I have another value which is supposed to be the actual total say 500. How do I adjust ...
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Are these populations non-random and different?

What would be the simplest, straightest-forwardest way to determine the following: Whether A,B,C is non-randomly distributed in each single group (IE: are there more A's in group 1 than random chance ...
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Test to prove two means do not have a difference

I have a population that I measure a value from once a day. I then made a change, and continued to measure that same value from the same population. What test could I use to prove that my change did ...