A professor believes that, for the introductory art history classes at his university, the mean test score of students in the evening classes is lower than the mean test score of students in the morning classes. He collects data from a random sample of 250 students in evening classes and finds that they have a mean test score of 88.1. He knows the population standard deviation for the evening classes to be 2.8 points. A random sample of 200 students from morning classes results in a mean test score of 88.8. He knows the population standard deviation for the morning classes to be 6.4 points. Test his claim with a 95% level of confidence. Let students in the evening classes be Population 1 and let students in the morning classes be Population 2. Step 2 of 3: Compute the value of the test statistic. Round your answer to two decimal places.