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.Assuming α = 0.05,which of the following is the appropriate critical value?

Question

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.Assuming α = 0.05,which of the following is the appropriate critical value?

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The Answer of 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.Assuming α = 0.05,which of the following is the appropriate critical value?