You want to predict the exam score of a student using the amount of time spent (measured in hours) preparing for the exam. You have collected a sample of 50 students. The sample regression line has an intercept of 17 and the slope of 18. For a student who spent 3.5 hours preparing for the exam whose actual exam score is 56, what is the prediction error?
Hint: Answer should be accurate to 1 decimal place.