To test the effectiveness of a business school preparation course, 8 students took a general business test before and after the course. The results are given below.

Exam Score

Exam Score

Student

Before Course (1)

After Course (2)

1

530

670

2

690

770

3

910

1,000

4

700

710

5

450

550

6

820

870

7

820

770

8

630

610

Referring to Scenario 10-5, the value of the sample mean difference is ________ if the difference scores reflect the results of the exam after the course minus the results of the exam before the course.