ude physical height and weight, along with temperature measured in Kelvin.</p>
<p>There are two important reasons that we must pay attention to the scale of measurement of a variable. First, the scale determines what kind of mathematical operations we can apply to the data (see Table <a href="working-with-data.html#tab:MeasurementTypes">2.2</a>). A nominal variable can only be compared for equality; that is, do two observations on that variable have the same numeric value? It would not make sense to apply o