In Professor Krugman's economics course, the correlation between the students' total scores prior to the final Which of the choices is correct interpretation of the slope in the context of the problem? examination and their final-examination scores is r = 0.5. The pre-exam totals for all students in the course have mean 280 and standard deviation 40. The final-exam scores have mean 75 and standard deviation 8. Professor Krugman has O For each point of a student's pre-exam score means an drop of 47 points on the final exam, on average. lost Julie's final exam but knows that her total before the exam was 300. He decides to predict her final-exam score from O For each point of a student's pre-exam score means an drop of 0.1 point on the final exam, on average. her pre-exam total. O For each point of a student's pre-exam score means an additional 47 points on the final exam, on average. O For each point of a student's pre-exam score means an additional 0.1 point on the final exam, on average. (a) Which of the choices is the least-squares regression line of final-exam scores on pre-exam total scores in this course? (b) Use a regression line to predict Julie's final-exam score. Give your answer as a whole number. Oj = 47 – 0.1x Oj= 47 + 0.1x Oj = -47 + 0.1x Predicted final-score = Oj = -0.1 – 47x (c) Julie does not think this method accurately predicts how well she did on the final exam. Select the statement that correctly uses r² to argue that her actual score could have been much higher (or much lower) than the predicted value. O Since r² = 0.25 is positive, then the regression line does not predict final scores very well. Julie could have a much higher score. O Since r = 0.25 is close to 0, then the regression line does not predict final scores very well. Julie could have a much higher or lower score. O Since r = 0.25 is not exactly Q then the regression line does predict final scores very well. Julie could have a much higher or lower score. O Since ² = 0.5 is close to 0, then the regression line does not predict final scores very well. Julie could have a much higher or lower score.