Skew

Q: How deeply does Machine Learning for Tabular Data: XGBoost, Deep Learning, and AI cover skew?

Defines right skew and demonstrates diagnosis with summary statistics, percentiles, filtering, and density visualization.

As explained in Machine Learning for Tabular Data: XGBoost, Deep Learning, and AI

A probability or empirical distribution that is asymmetric around its central tendency.

Skew describes an asymmetric distribution. A positively skewed target has a concentrated lump of values and a long tail extending to the right. In exploratory data analysis, comparing the minimum, mean, maximum, and selected percentiles reveals whether extreme values are distorting the apparent range. section 7.1.6

A practical check for skewed regression targets:

Inspect minimum, average, and maximum values. section 7.1.6
Compare extreme percentiles, especially the 95th, 99th, and maximum values. section 7.1.6
Plot the density and median to distinguish a long tail from a separate high-end cluster. section 7.1.6
If appropriate for the analysis, focus on the core range by filtering extreme lower and upper observations. section 7.1.6

Accommodation-price target

A target with a minimum of 1,450, an average of 36,573.1, and a maximum of 1,306,500 contains unusually large values. Its 99th percentile is 304,531.4, far below the maximum. After retaining values from 5,200 to 84,857, the density plot shows a right-skewed distribution and a possible small cluster of high-end accommodations. section 7.1.6

How Machine Learning for Tabular Data: XGBoost, Deep Learning, and AI covers it

Cover of Machine Learning for Tabular Data: XGBoost, Deep Learning, and AI

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Also explained in

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Effective Data AnalysisSkewness is the degree and direction to which a distribution is asymmetric around its center.
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Modern CSkew is a statistical measure of the asymmetry or lopsidedness of a distribution.
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Modern C, Third EditionSkew measures the asymmetry or lopsidedness of a distribution around its mean.
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Statistics Slam DunkSkewness is the asymmetry of a probability distribution around its center.

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Related concepts

symmetrymeasures · Symmetry is the preservation of relevant structure or properties under a specified transformation, such as reflection, exchange, or reversal.
log transformationaddressed by · A log transformation maps numerical values through a logarithmic function, changing their scale and often compressing large values or converting multiplicative relationships to additive ones.
Gini coefficientcontrasts with · A Gini coefficient is a summary measure of inequality derived from the area between a Lorenz curve and the line of perfect equality, typically ranging from zero for complete equality toward one for greater inequality.
density plotmeasured by · A density plot is a visualization that estimates and displays the shape of a continuous variable’s probability distribution as a smooth curve.
raw momentproduced by · A raw moment is a statistical quantity formed from a specified power of observations measured relative to zero, typically by summing or averaging those powers.
right-skewed distributionmeasures · A right-skewed distribution has most probability mass or observations at lower values and a comparatively long tail toward higher values.

This explainer was generated by Manning's knowledge graph from the text of Machine Learning for Tabular Data: XGBoost, Deep Learning, and AI. The section links point to the parts of the book it draws on.