8. The heights (in cm) of an SRS of nine children are given below at their 11th and 12th birthdays: Child 1 2 3 11th Birthday 113 12th Birthday 116 119 120 4 5 106 105 106 118 111 109 110 122 6 7 116 103 115 8 9 119 109 121 Find a 95% confidence interval for the average growth of children between the ages of 11 and 12. State any assumptions you need to make.