A Tutor Promises to Improve GMAT Scores of Students by More

question 34

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 is the correct value of the test statistic?

• A) z = 1.7143
• B) z = 1.7500
• C) t₄₈ = 1.7143
• D) t₄₈ = 1.7500

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