In an effort to determine the most effective way to teach safety principles to a group of employees, four different methods were tried. Some employees were given programmed instruction booklets and worked through the course at their own pace. Other employees attended lectures. A third group watched a television presentation, and a fourth group was divided into small discussion groups. A high of 10 was possible. A sample of five tests was selected from each group. The test grade results were:

Sample Number Programmed Instruction Lecture TV Group Discussion
1 6 8 7 8
2 7 5 9 5
3 6 8 6 6
4 5 6 8 6
5 6 8 5 5

At the 0.01 level, what is the critical value?