With this at hand, we can say that we are 95% confident that the true difference between the online and face-to-face groups falls between -8.37 and -1.44. We can also construct a z statistic by dividing the difference in mean by the $SE\$ of the differences.
In section Hypotheses Test, in paragraph:
With this at hand, we can say that we are 95% confident that the true difference between the online and face-to-face groups falls between -8.37 and -1.44. We can also construct a z statistic by dividing the difference in mean by the $SE\$ of the differences.
has a typo near the end: $SE\$, instead of $SE$