<p>In <a href="https://github.com/mlpack/mlpack/pull/742#discussion_r72756774">src/mlpack/methods/preprocess/preprocess_describe_main.cpp</a>:</p>
<pre style='color:#555'>&gt; + * @param rowMean Mean of the given vector.
&gt; + * @return Skewness of the given vector.
&gt; + */
&gt; +double Skewness(const arma::rowvec&amp; input,
&gt; +    const double&amp; rowStd,
&gt; +    const double&amp; rowMean,
&gt; +    const bool population)
&gt; +{
&gt; +  double skewness = 0;
&gt; +  double S3 = pow(rowStd, 3);
&gt; +  double M3 = SumNthPowerDeviations(input, rowMean, 3);
&gt; +  double n = input.n_elem;
&gt; +  if (population)
&gt; +  {
&gt; +    // Calculate Population Skewness
&gt; +    skewness = n * M3 / (n * n * S3);
</pre>
<p>Why not just write</p>

<p><code>skewness = M3 / (n*S3);</code></p>

<p>Besides, according to the formula at this <a href="http://www.macroption.com/skewness-formula/">page</a>, I think the equation of population skewness should be</p>

<p><code>std::sqrt(n) * M3 / (n*S3);</code></p>

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