Exhibit 10

question 45

Multiple Choice

Exhibit 10.9.A tutor promises to improve GMAT scores of students by more than 50 points after three lessons.To see if this is true,the tutor takes a sample of 49 students' test scores after and before they received tutoring.The mean difference was 53 points better after tutoring,with a standard deviation of the difference equal to 12 points.Let denote the mean of the difference: score after tutoring minus score before tutoring. Refer to Exhibit 10.9.What is the appropriate conclusion at the 5% significance level?

• A)Reject ,we can conclude that the mean difference in test scores after and before tutoring is greater than 50 points.
• B)Reject ,we cannot conclude that the mean difference in test scores after and before tutoring is greater than 50 points.
• C)Fail to reject ,we can conclude that the mean difference in test scores after and before tutoring is greater than 50 points.
• D)Fail to reject