Tis hypothesized that children who had survived a brain tumor were more likely to have behavioral and emotional difficulties than were children who had not experienced such trauma. to test this hypothesis, 40 children who all had survived a brain tumor participated in a study. parents of the children rated their own child’s behavioral difficulties. the mean rating was 10.1 with a standard deviation of 3. this data was compared with the known population ratings from children who had not suffered a brain tumor, which were 8.7 with a standard deviation of 2.8. what statistic should be used to determine if children who have survived a brain tumor are more likely to have behavioral difficulties than children who have not experienced such a trauma?