Marks in two subjects, A and B, are scaled to have a normal distribution. The marks obtained by 8 students in exam A have mean 54. The marks obtained by the same 8 students in exam B have mean 59. The standard deviation of the differences in their marks is 6.3 . The absolute value of the test statistic for comparing means is (2dp) Marks in two subjects, A and B, are scaled to have a normal distribution. The marks obtained by 8 students in exam A have mean 54. The marks obtained by the same 8 students in exam B have mean 59. The standard deviation of the differences in their marks is 6.3 . The absolute value of the test statistic for comparing means is (2dp)