Skewness measures (or refers to) a degree of asymmetry in the distribution of a variable.

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Statistical test to compare skewed distributions of binary data

I have two positively skewed distributions of binary data (0, 1) I would like to compare. I'm not an expert of non normal distributions. Is there a statistical (R based) test to do this? Thanks in ...
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34 views

How to analyze this positively skewed data?

I am having trouble analyzing my dataset consisting of the sumscores of a questionnaire. For each item, subjects had to indicate whether they performed this behavior 'never', 'sometimes', or 'often', ...
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How to add time estimates

Imagine I have a bunch at tasks to complete sequentially. There is some uncertainty about how long each task will take to complete. So for each task, we might estimate a 50% chance that it can be ...
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46 views

Quantify the asymmetry of a one dimensional vector

I have image data, which I can represent as one dimensional vectors. Each value represents the brightness of a pixel in a line. eg: (1, 12, 4, 3, 1, 4) I want ...
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10 views

analysing improvement in ordinal score in a group before and after an intervention

I am looking for direction in how to analyse ordinal data in a sample before and a sample after an intervention. I have performed an audit of safe drug syringe labelling practice in surgery before ...
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20 views

On skewed distributions, should the test/train/cross validation set be similar to the real set

On a skewed distribution (say there are two classes and the distribution is 2%-98%), given the small number of examples of one of the classes, would it be correct to have them distributed 50%-50% for ...
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28 views

Difficulty in calculating skewness

I'm trying to quantify the skewness of the distribution of random integer variable, generated in the interval from 1 to 15, with a function that I wrote in C++. Here are the generated values: ...
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120 views

Skewness Kurtosis Plot for different distribution

I am looking for a way to plot a skewness kurtosis plot of a range of distributions: Pearson systems, log normal, gamma , generalized gamma, Pareto 1,2,3,4 etc. I've only found some of these ...
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44 views

Multivariate asymmetric generalized gaussian distribution

I would like to write the distribution of a multivariate asymmetric generalized gaussian distribution and plot the result with Matlab. So far I was able to write the code to create a bivariate ...
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40 views

Right skewed asymmetric Gaussian-like distribution

I am trying to find a possible candidate as a fitting function for a distribution that looks like the following I know that this isn't a straightforward question, but I would like a simple function ...
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19 views

Skewed population example

"Consider a strongly skewed population (e.g., waiting times at airport security screening)." My book always uses that example when referring to skewed populations. I don't understand why would ...
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25 views

testing dependent skewed samples

I must compare two distributions of patent data: namely, they are the number of patent applications of companies before vs after an acquisition. I need to perform an hypothesis test to assess if the ...
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79 views

Plot a highly skewed dataset

I have a dataset that contains music genres, songs and a "speechiness" rate. An example looks like this: ...
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75 views

Getting expected value from Standard Deviation and Skew?

If I have: - Standard deviation - Skew What additional information can I calculate ? Could I calculate Expected Value?
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48 views

Good Multivariate normality coefficient but suspicious univariate indices in AMOS, what to do?

We are conducting a research with 15 observed variables. Before starting a SEM model based on our data-set (of 531 cases), we tried to check for uni-variate & multivariate normality problems. The ...
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16 views

Normalizing logarithmic data in a range from 0 to 1

i am replicating a multilevel-analysis for my bachelor thesis (with newer data + corrections). The author i am citing used the unstandardized coefficients of every independent variable as beta ...
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18 views

Extended Standard Deviation - like functions, Skew, Kurtosis

I am gathering some performance data, and am doing the obvious storing the sum and sum of squares so I can calculate mean and deviation. And that would describe a normal distribution quite well. But ...
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42 views

Gaussian distribution sample norm versus mean norm

Consider a Gaussian distribution with mean $\boldsymbol\mu$ and covariance matrix $\mathbf{Q}$, and suppose I take a sample from this distribution and compare its norm with the mean norm. My goal is ...
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46 views

How to model these data? (zero inflated, positive skew,

- The variable depicted in the histogram is a sum of 11 items. Each item asks about the frequency of occurrence of a particular type of event (a negative consequence of drinking) on the following ...
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41 views

Removing outliers from asymmetrical, multivariate, categorical data?

I'm doing a project which asks the question of whether common ivy (Hedera helix) is more abundant on some species of tree than others. I did several transects and looked at each tree within the ...
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49 views

Testing for significant differences in skewness

How do you test for significant differences in skewness across two distributions of citation data, using R? I'm trying to compare the two power-law distributed histograms below (I'm just using ...
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38 views

Relationship between correlation and coskewness

If C is a NxN correlation matrix of a N variables and s is vector of N univariate standard deviations for those variables, we can compute covariance matrix by: S = s'sC Is there a way to compute ...
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12 views

Finding Anomalies in skewed data

I have the following highly skewed variables Each data point represents an observation and I'm trying to find observations that are not like the others. For each variable, I tried finding outliers ...
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110 views

Skewness - why is this distribution right skewed?

If I interpret the accepted answer here correctly, I would say that the distribution below is right skewed (because of the points above the straight line on the far right). I don't really understand ...
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33 views

Examining interactions when one group is normally distributed and the other is not

I'm running regressions on some data so I checked to see if the data was normally distributed. I need to create interaction terms using gender so I split the variables by gender and examined them. ...
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101 views

What do I fit to a heavily positively skewed histogram?

I have a data which has heavily positively skewed variables. My manager has told me to fit it some distributions (univariate). The problem is that for most of the data the mean is far closer to the ...
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58 views

Two-sample Kolmogorov-Smirnov test with errors on data points

Short version I want to test if two samples, which follow a skewed distribution, can be distinguished from each other. A Kolmogorov-Smirnov statistic for two samples would be sufficient if there was ...
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37 views

How to analyse a distribution with some given sample moments?

Suppose that I have n observations, $$X_1,...,X_n$$ with unknown distribution, n being small (say, between 6 and 20). If I know the first four sample moments (average, standard deviation, skewness, ...
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What purpose does multiplying by 3 serve in Pearson's second coefficient of skewness?

It can be calculated by $\frac{3\,(\text{mean}-\text{median})}{\text{standard deviation}}$. Does the 3 make the result easier to work with somehow, or what?
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How to deal with skewness that is due to the specific sample?

For my master's thesis, I am performing regression analysis on my data, where perceived performance on a task was used as the DV (7-points scale, 7 being the highest perceived performance). The sample ...
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97 views

Normalization of a data with skewed distibution

I have a data set which has 10 features (columns). I want to normalize the data before dealing it with deep learning. Each column has a different distribution but overall they are all skewed! 1) ...
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42 views

Similarity measures between bimodal distributions

I have to compare two bimodal distributions. So far, I have found the Bimodality Coefficient: $$ BC = \frac{\mu_{3}^{2} + 1}{\mu_{4} + 3\frac{(n-1)^2}{(n-2)(n-3)}}, $$ with $\mu_{3}$ referring to ...
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Which transformation to apply on a skewed distribution?

Should each feature be transformed to a normal distribution in each and every case or it depends on the classifier or other factors ? First of all how do we conclude that data is skewed and if it is ...
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159 views

Skewness, kurtosis and how many standard deviations values are from the mean

As is well known for the normal distribution, 68% of the probability mass is within one standard deviation of the mean, 95% within two standard deviations and 99.7% within 3 standard deviations. ...
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39 views

Transforming a skewed data set to a Normal distribution

Say there is a skewed data set with a average of 35 and max and min points are 55 and 12 respectively. I want to know whether it is possible to transform this data set to a normal distribution so that ...
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130 views

Clustering: Do I have to transform all variables derived from a single categorical variable in the same way?

Basic problem Here is my basic problem: I am trying to cluster a dataset containing some very skewed variables. The variables contain many zeros and are therefore not very informative for my ...
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Are two samples with skewness equal?

I have two samples, my hypothesis is that both of them are equal. The number of experiments is different (N), the means are very similar and the medians are 5 and 4. First I calculate descriptive ...
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Can we always rewrite a right skewed distribution in terms of composition of an arbitrary and a symmetric distribution?

Consider a twice differentiable and symmetric distribution $\mathcal{F}_X$. Now consider a second twice differentiable distribution $\mathcal{F}_Z$ rigth skewed in the sense that: ...
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51 views

Interpreting Skewness

I'm reading Dr. Shewhart and Wheeler's books, and neither think skewness has value in statistics. When discussing the central tendency of two independent data sets that share a commonality, like ...
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Estimating medians and modes of skewed distributions using GLMs

Edited question (less vague hopefully) I am wondering why for generalized linear models with Gamma, Poisson and Negative Binomial distributions that there appears to be no discussion about estimating ...
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measure of multivariate skewness

I am looking for a generalization of Pearson's or the Yule-Kendall's skewness measures, from univariate to multivariate data. If not a proper generalization, any other measure sensitive to the ...
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Is it possible for a random variable with 0 mean to have a positive expectation after compounding many observations?

Basic example, assume that the expected daily return of the S&P 500 stock market index is 0, i.e., the return on any given day of the stock market is 0.0%. But, we also (generally) expect that ...
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How to analyse skewed and unskewed data on SPSS?

Study design: I have shown participants a series of photos of themselves vs. other people's bodies (original and manipulated), and asked them to find the original. Their responses were recorded and ...
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66 views

How to scale a skewed-distribution predictor for a neural network?

I’d like to ask what would be the more appropriate way of introducing a predictor variable with a highly skewed distribution into a neural network model. Suppose I had a variable whose distribution ...
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92 views

Creating a probability distribution that is truncated skewed

I have a dataset I want to use to generate a probability distribution. The distribution is skewed and can only include positive integers. I've tried normal (both skewed and truncated, although I ...
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111 views

Testing for normality in non-normal distributions with zero skewness and zero excess kurtosis

[This question was formerly called "On Non-normal distributions with zero skewness and zero excess kurtosis" and relabeled to better reflect its focus.] I am trying to write a little simulation using ...
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82 views

How to analyze skewed and unskewed data on SPSS?

Study design: I have shown participants a series of photos of themselves vs. other people's bodies (original and manipulated), and asked them to find the original. Their responses were recorded and ...
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0answers
7 views

Skewness and metrics for selection

Considering results of an experiment of examining 2 different methods against 152 samples, grouped in 8 groups. Also assuming that we acquired the skewness value for each group. If we are willing to ...
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138 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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Comparing several asymmetric distributions

I have constructed 3 toy distributions using R ...