1) In a random sample of 50 students, the average income is found to be 6,500. The income is known to be normally distributed with population standard deviation 1000. Find the 95% confidence interval for the income of students. Round to the nearest hundredth.
2) In a random sample of 30 people, the mean height is 68.4 inches and the sample standard deviation is 4.2 inches. The population standard deviation is not known. Find the 95% confidence interval for the heights. Round to the nearest hundredth.
3) For a random sample of 50 students, it is found that 75% travel for spring break. Find the 95% confidence interval for the proportion of students who travel for spring break. Round to the nearest hundredth.