A Tutor Promises to Improve GMAT Scores of Students by More

question 126

Multiple Choice

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 µ_D denote the mean of the difference: score after tutoring minus score before tutoring. Which of the following hypotheses will determine if the students improved their test scores by more than 50 points after being tutored?

• A) H₀: µ_D ≤ 0, H_A: µ_D > 0
• B) H₀: µ_D ≥ 0, H_A: µ_D < 0
• C) H₀: µ_D ≤ 50, H_A: µ_D > 50
• D) H₀: µ_D ≥ 50, H_A: µ_D < 50

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