Questions tagged [group-differences]

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

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Dependent tests?

I have 3 independent data groups: A, B, C. I performed t-test on each pair of groups: AB, AC and BC. So these three tests (AB, AC, BC) are not independent, are they? Thanks for answer!
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139 views

What statistical tests would you recommend for group difference for my data?

I am trying to find out what statistical tests to run on a set of aggregate data (no individual data) on 3 different groups, variables are summarized below: Group 1 in site 1: Mean value (blood sugar) ...
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1answer
4k views

Comparing distributions of unequal sample sizes

Consider the distribution shown in the below histogram: I have computed a Welch's t-test for a difference in means between these two groups, as well as a Kruskall-Wallis test to see whether these two ...
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1answer
155 views

How can I reproduce TukeyHSD's difference of means?

My data set comes from a series of five three-way full-factorial experiments, several of which are unbalanced. The three experimentally manipulated factors have two levels each. I am using R to ...
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0answers
12 views

Best way to score pair differences

I'm fairly clueless how to accomplish my goal here... Firstly a bit of back story: I have about 10 technicians, and they each make sets of concrete samples in the field. Each sample has 2 x 28 day ...
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1answer
19 views

Adding two outcomes and comparing with a third outcome

I did two experiments, with component A and component B respectively, and the outcome that I have is "mass loss" for those two components. Now, there is a third experiment where both components are ...
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270 views

Hodges-Lehmann estimator as a percentage?

I'm comparing samples X and Y (of sizes M and N respectively). I need to report whether the samples are statistically different (Mann-Whitney U-test) and by how much (Hodges-Lehmann estimator) to ...
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1answer
269 views

SEM and group invariance: Can I get modification indices for freed parameters using R-package Lavaan

I'm learning structural equation modeling with R and lavaan package. MPlus (other software for SEM models) can print an output indicating what would the effect if ...
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1answer
61 views

Bonferroni correction when comparing sub-group with rest of the group

I am working with 4 machines that test products and record a value during each test. I have ~ 1000 records from each, and some recorded values look like: -0.67, 0.3, 5.7, 2.3, -0.78, 5.2, 5.8, 9, 2.1,...
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1answer
84 views

Analysis for two groups tested at two different times

I have a dataset with 50 items divided in two groups: placebo (P) and diet (D). Each group has 25 items. Items were weighted once at two different times: at t0 (before treatment) and t1 (after ...
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0answers
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Validity of conclusion of statistical tests when comparing two groups of observations in an experiment

I am just reading the results of an experiment, and I am having a hard time estimating their validity. In the experiment, several participant had to perform a certain task twice, once with the ...
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42 views

Am I violating assumptions of mixed effects model?

I am using a mixed effects model to analyse data, but am unsure whether I am committing any violations due to the nature of the data I have. My data comes from a game whereby people have to identify ...
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1answer
310 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 ...
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1answer
197 views

How to handle regression with unequal sample size and variance?

Let's say that I have 10,000 people do a study, and in this study they have to spot a bird in a scene as quickly as possible. There are various possible birds that may be presented to each person, and ...
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1answer
488 views

Principal component analysis with non-independent observation

I have observations with 6 individual-level characteristics from 2000 units in 56 groups (villages). I know that within groups, characteristics are strongly related as individuals influence each other....
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44 views

Mean comparizon of two groups - Asymptotic distribution

Let $\{X_1,\ldots,X_{n_1}\}$ and $\{Y_1,\ldots,Y_{n_2}\}$ be sequences of independent and identically distributed random variables, such that $EX_i = \mu_X$, $VX_i = \sigma^2<\infty$, $EY_j = \...
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1answer
54 views

One predictive model for all data vs subject/group specific models

I noticed that in some (rare) situations, training subject/group/subpopulation specific models is preferred to one general predictive model for all data (probably due to accuracy?). For example, in ...
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417 views

Bayesian Proportion Test … with Cumulative Successes and Trials?

I am conducting a Bayesian Proportions Test (using R's BayesianFirstAid package) of consumer conversion rates at different ad impression frequencies. Conversions are considered successes and ...
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1answer
198 views

Different results doing mixed effects anova and post hoc tests of simple effects and paired T-test

I have run a mixed effects anova in r to look at the performance differences in two groups (control, patient) in 5 separate conditions. The conditions are my within subject factors. Group is the ...
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1answer
59 views

Why do we need to know the underlying distributions to check if two sets of paired values are significantly different (e.g. t-test)

I know this is an extremely basic topic for most of you, but I am wondering why we need to assume an underlying distribution to tell whether two sets of paired values are significantly different or ...
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3answers
131 views

Is Function of Random Samples of Two Independent Populations I.I.D.?

I want to bound the difference between two variables sampled from two different populations. When it's just one population with paired measurements a.k.a. "paired samples" (e.g. before treatment vs ...
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53 views

Population Treatment estimate from multiple uneven groups

I have a number of different groups (on the order of 100). Each has many members (on the order of 1000) but the groups are all different sizes and range from 100 to 1000+ in size. Each of these ...
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1answer
53 views

Can I still apply statistics to this problem?

I've an ongoing experiment. We're trying to determine if it's possible to detect if a bunny is infected with a disease through an electronic device over a period of time of 1 month. Since we couldn't ...
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50 views

Conclusion about between-groups differences in the absence of a baseline comparison

Many psychology studies draw conclusions from experiments that follow a design along the lines of: take two groups, and subject each of them to a different manipulation (e.g. task instructions etc) ...
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1answer
713 views

Can I perform two-sample t-test on z-scores?

I want to test for a difference in means between two sets of data. The data is standardized using $(X-\mu)/\sigma$. Can I perform two-sample t-test for a difference in means? In general, since I have ...
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121 views

Normalizing group data for correlation

Say I own gas stations across the entire north east and my total territory is broken down into regions. Some regions may have 100 gas stations and others may have 500. So the regions that have 500 ...
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109 views

Time series group comparison

I am currently analyzing a time-series experiment and I have some difficulties to come with a nice comparison of my groups. I was hoping someone could help me. The design is the following: Three ...
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2answers
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 ...
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1answer
89 views

Division of beta coefficient by p-value

Let's say I have results of a mesurement for a large number of treatments (p-value, beta, t-stat) on samples from a large number of different populations, and I want to compare how different the ...
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1answer
177 views

Is it valid to do a mixed ANOVA with one within and one between subjects factor when the between subjects grouping factor has very unequal groups?

I am doing a mixed ANOVA in SPSS where I am currently comparing the duration of certain script handwriting in 2 conditions (1=eyes open and 2=eyes closed) for the same 40 participants in both ...
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0answers
101 views

Determine Chi Square Group Differences in multiple choice questionnaire

I'm trying to determine if there is a group difference in answering a multiple choice question. For example, I want to answer the question of, do "Change Instigators" (group A) answer "communication"...
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1answer
44 views

Testing difference between group of values

I have n series of values as follow. Let's say they are scores of students in a class (just example) ...
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273 views

Repeated Measures in SEM

I would have a question about using Structural Equation Modeling for comparing repeated measures results. I have a one DV which has been measured 4 times and corresponds to 4 different experimental ...
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1answer
82 views

Is it possible to compare 2 groups while controlling for something?

Is it possible to compare two groups (e.g., t-test, Wilcoxon, Mann-Whitney test, etc.) while controlling for something? E.g., I want to compare home ownership between military veterans and non-...
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1answer
82 views

statistical test for analyzing survey data

One question of my survey (n=468) was to indicate on a scale from 1 to 5 how well they know our government. My hypothesis is that women know our government better than men. What statistical test do I ...
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1answer
441 views

Comparing the degree of similarity between groups

I have three groups A, B and C and I want to prove that similarity between group B and group A is significantly higher than between group B and group C. How to prove it? Simple example: I have ...
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1answer
516 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 ...
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3answers
3k views

How to group/cluster similar words

Let say I have a list of words, such as: apple apale aaple apples oranges ornnges orange orage melons meeons meeon melon melan I want to group them based on ...
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65 views

Minimal Detectable Change for population surveys

I am wondering if it would be possible to calculate the Minimal Detectable Change when examining 2 population surveys? I know how to calculate the MDC in a test-retest situation in which every ...
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1answer
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Differential Expresion Comparisons

In a Differential expression experiment concerning a gene of interest there is an upregulated condition, downregulated condition and control. When comparing these, it obviously makes sense to compare ...
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292 views

What is the null distribution of the between-group variance?

Scenario From a population, we randomly sample $n$ individuals, measure the normally distributed random variable $X$ and compute the total variance $V_T$ of $X$ in this sample. Then, we randomly ...
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How to treat subsamples that differ in respect to the dependent variable prior to any treatment?

I have conducted an experiment on a sample that consisted of both male and female students to see if a specific emotion influences moral judgment. My research goal didn't involve any hypothesis about ...
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1answer
64 views

Comparing capture rates in 2 groups: which test?

I am comparing rate of capture (animal captures per hour) between two years. I'm interested in determining whether there is a difference between rate of capture between the two years. A survey night ...
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0answers
123 views

Permutation test for equality between the distribution of $g$ population

I have a data matrix of 42000 observation and 12 variables I suppose to observe 12 samples of size $n_j$ from 12 indipendent random variables $Y_j,j=1,...,g$ I want do a permutation test for $$H_0: ...
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2answers
240 views

What is the difference between doing a linear regression and exhaustive descriptive statistics?

I'm doing a report of the differences between women and men in their performance on a test with variables like: age, education, race and of course genre. I have two options: doing a linear regression ...
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1answer
188 views

How to deal with dropouts from a waiting list control group?

Many treatment studies compare a treatment group with a waiting list control group, for example to adjust for spontaneous remissions. Unfortunately, many more participants drop out from the waiting ...
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0answers
200 views

Difference in differences in proportions statistical test

I am running a case-control interventional study where the dependent variable/ outcome is a proportion. The cases were given an intervention whereas the controls were not and measurements were taken ...
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2answers
104 views

Compare in-pairs differences to between-pairs differences

I have some numerical data which comes in pairs. I need to test the hypothesis that values inside pairs are more similar to each other, than to other values in the sample. Is there a test for this?.. ...
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0answers
68 views

How to compare three groups ranking a set of items?

I have six photos which the test subjects rank according to their preference. So the response per person is six columns, "Rank of photo A" to "Rank of photo F". I am grouping the subjects by religion,...
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2answers
854 views

Cook's distance in detecting outliers

According to my understanding, Cook's distance measures the influence of each observation by excluding points when fitting a model. So I assume it could be an reasonable approach for outlier detection?...