.
Variables for comparison:</p><ul><li><p>variable : character. numeric variable name</p></li>
<li><p>train_mean : numeric. arithmetic mean of train set</p></li>
<li><p>test_mean : numeric. arithmetic mean of test set</p></li>
<li><p>train_sd : numeric. standard deviation of train set</p></li>
<li><p>test_sd : numeric. standard deviation of test set</p></li>
<li><p>train_z : numeric. the arithmetic mean of the train set divided by
the standard deviation</p></li>
<li><p>test_z : numeric. the arithmetic mean 