Different teachers using different methods taught two groups of students. Both groups of students sat the same examination at the end of the course. The students' marks are shown in the grouped frequency table. a Work out an estimate of the mean mark for Group A and an estimate of the mean mark for Group B. b Write down whether or not the answer to a suggests that one method of teaching is better than the other. Give a reason for your answer. Exam Frequency Frequency Mark Group A Group B 20-29 1 1 30-39 3 2 40-49 6 4 50-59 6 13 60-69 11 15 70-79 10 6 80-89 8 3 AppendixLO1