Unit 4 Data Files http://glencoe.mcgraw-hill.com/sites/0078786051/student_view0/data_files.html
Unit 4 Lesson 2 Interactive Review http://glencoe.mcgraw-hill.com/sites/0078786051/student_view0/unit4/lesson2/interactive_reviews.html
Unit 4 Lesson 2 Self-Check http://glencoe.mcgraw-hill.com/sites/0078786051/student_view0/unit4/lesson2/self_checks.html