Tagged Questions

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

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25 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 ...
3
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1answer
64 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 ...
2
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1answer
22 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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0answers
14 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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0answers
26 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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0answers
18 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 ...
1
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1answer
69 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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0answers
8 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 ...
2
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0answers
24 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 ...
0
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1answer
31 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 ...
1
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2answers
31 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 ...
1
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0answers
28 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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0answers
28 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 ...
0
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0answers
61 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 ...
0
votes
2answers
38 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 ...
0
votes
1answer
41 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 ...
2
votes
2answers
68 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 ...
1
vote
1answer
33 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 ...
0
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1answer
48 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 ...
2
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0answers
52 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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0answers
11 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 ...
1
vote
1answer
51 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 ...
1
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1answer
151 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 ...
1
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0answers
34 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 ...
6
votes
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
votes
1answer
105 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 ...
0
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0answers
23 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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0answers
33 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: ...
0
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0answers
19 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 ...
0
votes
1answer
104 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 ...
2
votes
2answers
109 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 ...
0
votes
1answer
35 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 ...
0
votes
1answer
32 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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0answers
79 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
84 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, ...
0
votes
1answer
33 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 ...
5
votes
1answer
73 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 ...
3
votes
0answers
48 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 ...
0
votes
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 ...
1
vote
2answers
105 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 ...
2
votes
2answers
64 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. ...
1
vote
2answers
43 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 ...
2
votes
1answer
21 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 ...
2
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0answers
96 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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votes
1answer
54 views

Best ARIMA Model

What ARIMA model would be the best fit for the data provided?: ...
1
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0answers
29 views

Detecting heterogeneity in groups

This is a mockup of a dataset I am currently working on: ...
0
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0answers
39 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 ...
1
vote
0answers
50 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 $Z = X - Y$?
2
votes
1answer
82 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". ...
3
votes
4answers
124 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 ...