I need some help on these three questions please :)

Jump to level 1 Suppose the mean height in inches of all 9th grade students at one high school is estimated. The population standard deviation is 3 inches. The heights of 8 randomly selected students are 66, 69, 61, 63, 70, 65, 68 and 74. a = Ex: 12.342 Margin of error at 90% confidence level = Ex: 1.23 90% confidence interval = [ Ex: 12.34, Ex: 12.34 [smaller value, larger value] 2