CHALLENGE ACTIVITY 6.2.1: Confidence intervals for population means. 270604.2050052.qx3zqy7 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 4 inches. The heights of 9 randomly selected students are 62, 64, 75, 65, 64, 70, 64, 72 and 62. T = Ex: 12.34 Margin of error at 95% confidence level = Ex: 1.23 95% confidence interval = [ Ex: 12.34 Ex: 12.34 [smaller value, larger value]