The correlation between the number of hours spent studying for a science exam by students (x) and their final exam scores (y) is found to be about r = 0.9. Suppose we use the hours spent on studying (x) by a student to predict the student's final exam score (y). We can say that: The fraction of variation in final exam score explained by the least-squares regression line of final exam scores on number of hours spent studying is 0.81. Number of hours spent studying is generally 90% of a student's final exam score. About 90% of the time, hours spent on studying will accurately predict the final exam score. The least-squares regression line of y on x would have a slope of 0.9