# Questions tagged [skewness]

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

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### Trying to determine which distribution to use for my percentage data for mixed effects model

I am seeing a lot of different answers to percentage data, either beta or binomial with a logit link and not to use poison distribution because it isn't count data. My response variable is retention ...
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### In R, how to detect possible outliers in right skewed data assuming Poisson distribution?

I am attempting to identify possible outliers in data which is skewed to the right and I assume it is Poisson distributed. I am a novice in all things statistics, and the following may be utterly ...
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### Which calculation is correct/used in which case for adjusted Skewness?

I was looking at the wikipedia page for skewness here: http://en.wikipedia.org/wiki/Skewness and under the section on sample skewness the following modification is shown for sample skewness: However,...
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### Using paired t-test or Sign test to compare two groups of correlated measures on the same subject?

I have conducted a survey where participants are shown 8 different advertisements: 4 of the ads attempt to evoke the feeling of guilt, 4 others attempt to evoke the feeling of shame. After seeing each ...
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### PDF Formula for distribution with mean, standard deviation, skew, and kurtosis

What would the probability density function be for a graph with input variables: mean, standard deviation, skewness, and kurtosis? For example, if the inputs were confined only to mean and standard ...
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### confidence interval for mean based on small sample when CLT does not hold

I have looked at similar questions but could not find an satisfactory answer. Please forgive if I'm wrong. I have a small sample (n = 24) and use the sample mean as estimator of the true mean. I want ...
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### Deriving skew t density function through convolution representation?

I am studying on skew t distribution, so i need its density function. I want to derive that via, integral of convolution representation. Could you please help me and introduce a good source?
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### Correlation between a normal distribution and a high positively skewed distribution

I would like to test the correlation between a quantitative continuous variable normally distributed (body mass index) and a quantitative continuous variable positively skewed (kurtosis=5, skewness=2)(...
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### Necessary to deal with skewness of response variable for Random Forest?

I am dealing with a regression problem for predicting the first-year production volumes of oil wells. My response variable is quite heavily right-skewed, as can be seen from the following distribution ...
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### Kernel for Skewness in U-statistics

How to find a kernel for a parameter \theta = E [(X-E[X])^3] and use it later for calculation of U statistics?
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### How to represent skewness(X) in terms of the expected value?

Let $X$ be the random variable. $E(X)$ is the expected value of $X$ Then $Var(X)$ = $E(X^2)$ − $[E(X)]^2$ where $Var(X)$ is the variance of $X$ Then how to represent skewness(X) in terms of the ...
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### Creating robust intervals from highly skewed data?

I am using factor analysis to model the underlying structure of social capital. My data consists of individual responses expressing how often they interacted with other individuals in a specific year, ...
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### Metric (distance) for highly skewed data

I am currently investigating some points in 4D in relation to some reference point (also in 4D). That is, I want to test how the distance to the reference point depends on some other variables. ...
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### How to deal with differently skewed biological data?

I have a single-cell data set with around 40 variables per cell (protein expression, all variables are measured simultaneously). The expression distributions for the single channels look quite ...
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### Skewness and kurtosis using quantiles and mean/variance

I would like to ask if there is a way to get skewness and kurtosis measures if we only know the distribution's mean, variance, and certain quantiles. Basically, the problem that I am facing is I have ...
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### Generate random values to mimic skewness

I have a actual set of data where the variables are heavily skewed, both positively and negatively. I need to generate random sample data for the values going forward. The data needs to be similarly ...
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### Estimating Quartiles with Moments

The Wikipedia article on Skewness indicates that the median of a distribution can be estimated from the mean, standard deviation, and skeweness with an error term that goes as $O(skewness^2)$. ...
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### How to conduct a test for independence in case of skewed classes (experiment design)?

The setting is as follows. We have a population of size $N$. Each subject has two properties $A$ and $B$, which can be either true or false. The question is: if for a random subject $A$ holds, is the ...
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### Performing t-test on highly skewed financial data + outlier treatment?

I need some advice on performing statistical tests on financial ratios and highly skewed data. I have gathered a large sample of several financial ratios for two groups. The sample size is + 40,000 (...
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### Z-score from Skewed Student T

I'm implementing the following method. The text is provided for background, but my question is about line (8). Am I understanding this as "a z-score generated from a standardized skewed Student t?" ...
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### R st.mple versus sstdFit versus python ss.nct.fit

Working through David Ruppert Statistics and Data Analysis second edition. Trying to determine difference between the st.mple output and the sstdFit output. ...
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### Skewness statistic - how close to zero should it be?

I am working my way through Chapter 3 in the Applied Predictive Modeling by Kuhn and Johnson. In section 3.2 the discussion values close to zero indicate symmetry. My question is - how close to zero? ...
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### Measuring the effect of a variable across a threshold

Within my data I am trying to assess whether the response variable increases as we move across different thresholds. The difficulty is that the response variable also increases exponentially as a ...
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### Modelling births as an outcome of population diversity as opposed to population size

I wish to model and estimate the relationship between population diversity and births (or birth rates) across populations, with panel data, and I face several challenges. 1) Births, population size ...
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### Log-Normalization of skewed data before feeding to neural network models ( autoencoders)

If your input data has few columns that are extremely skewed, It is well known that one would log normalize ( take log and then normalize or standardize) the data before passing to regression ...