Skew

As explained in Modern C

Skew is a statistical measure of the asymmetry or lopsidedness of a distribution.

A set of 20 run times ranges from 0.1 to 1.3 seconds, with a mean of 0.6 seconds. The spread is large: its standard deviation is 0.31 seconds, or 52% of the mean. Repeated measurements need more than a single average to describe them. section 15.3

Figure 15.1. Frequency histogram for our sample, showing the frequency with which each of the measured values was obtained

The frequency histogram shows how often each measured run time occurred, making the sample’s shape visible. section 15.3

TAKEAWAY: Skew describes the asymmetry of a distribution. It is an optional statistic alongside the number of measurements, mean, and standard deviation. Standard deviation describes spread; skew addresses whether that spread is lopsided. The sample illustrates why timing results need inspection, but no skew value is given for it. section 15.3

A C statistics collector can accumulate up to the third moment, providing a route to statistics beyond the mean and spread. The displayed timing report prints the mean and relative standard deviation, not skew. section 15.3

How Modern C covers it

How deep it goes

Mentions skew among timing statistics and shows third-moment collection, but gives no skew calculation or sample value.

Examples

Uses 20 timings from 0.1 to 1.3 seconds and a frequency histogram, without calculating their skew.

What you can do after

Evaluate/understand skew as a possible check on asymmetry in repeated timing results.

How it connects

Connects skew to frequency histograms, mean, standard deviation, and third-moment statistics.

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Also explained in

• 

  liveBookmanning.com
  Effective Data AnalysisSkewness is the degree and direction to which a distribution is asymmetric around its center.
• 

  liveBookmanning.com
  Modern C, Third EditionSkew measures the asymmetry or lopsidedness of a distribution around its mean.
• 

  liveBookmanning.com
  Statistics Slam DunkSkewness is the asymmetry of a probability distribution around its center.
• 

  liveBookmanning.com
  Machine Learning for Tabular Data: XGBoost, Deep Learning, and AIA probability or empirical distribution that is asymmetric around its central tendency.

Compare how 5 books explain skew →

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 Modern C. The section links point to the parts of the book it draws on.