 original values. The <strong>standard deviation</strong> aims to provide a more interpretable measure of spread, by transforming the variance back to the scale of the original values. The standard deviation of a collection of observed values, usually denoted as <span class="math inline">\(S_Y\)</span>, is simply the square-root of the variance, so
<span class="math display">\[S_Y = \sqrt{S^2_Y}\]</span>
or written out in more detail as
<span class="math display" id="eq:definition-sample-standard-deviation"