One hundred teachers attended a seminar on mathematical problem solving. The attitudes of representative sample of 12 of the teachers were measured before and after the seminar. A positive number for change in attitude indicates that a teacher's attitude toward math became more positive. The twelve change scores are as follows.

3; 8; 1; 1; 0; 4; 3; 2; 1; 5; 4; 2

• Part (a)What is the mean change score? (Round your answer to two decimal places.)