In an effort to improve scores on college-entrance exams, the principal at a large high school chooses 35 students at random who have already taken the exam. The students are enrolled in a six-week prep course to improve their scores. After the prep course, the students take the college-entrance exam again. The mean difference open paren first minus second close paren in exam scores is negative 1 point 7 5 points with a standard deviation of 7 point 1 2 points. Assuming the conditions for inference are met, what is the test statistic for testing the hypotheses ratio of cap h sub 0 to mu sub diff is equal to 0 ; ratio of cap h sub A to mu sub diff is less than 0 ?