I have answered all of these problems, except the last one question (d). It is incorrect and I'm not sure what I'm doing wrong. Please explain. Thank you.

One hundred teachers attended a seminar on mathematical problem solving. The attitudes of a representative sample of 1212of 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 1212change scores are as follows:

2;9;1;2;0;5;-4;1;1;6;4;2

(a) What is the mean change score?

Round your answer to two decimal places.

x= 1.75

(b) What is the standard deviation for this sample? Round your answer to two decimal places.

s=3.72

(c) What is the median change score? 1.5

(d) Find the change score that is 2.2 standard deviations below the mean. Round your answer to two decimal places.

I answered -6.50 and that answer is wrong. I am wondering what the correct answer is?