14. for which group of students—those who completed the test preparation course or those who did not…

Brief Explanations:

To determine which group has more variable test - scores, we would typically look at measures of variability such as the range, variance, or standard deviation. If the data for each group (test - preparation course completers and non - completers) is available, the group with the larger range, variance, or standard deviation has more variable test scores. A larger range means a greater spread between the highest and lowest scores. Larger variance or standard deviation values also indicate greater dispersion of scores around the mean.

Answer:

We need to calculate measures of variability (range, variance, standard deviation) for each group. The group with the larger value for these measures has more variable test scores.