n.
</p>
</dd>
<dt><code>chas</code></dt><dd>
<p>Charles River dummy variable (= 1 if tract bounds river; 0 otherwise).
</p>
</dd>
<dt><code>nox</code></dt><dd>
<p>nitrogen oxides concentration (parts per 10 million).
</p>
</dd>
<dt><code>rm</code></dt><dd>
<p>average number of rooms per dwelling.
</p>
</dd>
<dt><code>age</code></dt><dd>
<p>proportion of owner-occupied units built prior to 1940.
</p>
</dd>
<dt><code>dis</code></dt><dd>
<p>weighted mean of distances to five Boston employment centres.
</p>
</d