s data frame contains the following columns:
</p>

<dl>
<dt><code>u</code></dt><dd>
<p>The 1920 population.
</p>
</dd>
<dt><code>x</code></dt><dd>
<p>The 1930 population.
</p>
</dd></dl>


<h3>Source</h3>

<p>The data were obtained from
</p>
<p>Cochran, W.G. (1977) <em>Sampling Techniques</em>. Third edition. John Wiley
</p>


<h3>References</h3>

<p>Davison, A.C. and Hinkley, D.V. (1997) <em>Bootstrap Methods and Their Application</em>. Cambridge University Press.
</p>

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