12. As part of a safety cheek, the Pennsylvania Highway Patrol randomly stopped 65 cars and checked their tire Pressure. The sample mean was 32 pounds per square inch with a sample standard deviation of 2 pounds per square inch. Develop a 98 percent confidence interval for the population mean. 13. A survey of 4000 college graduates determined that the mean length of time to earn a bachelor's degree is 5.08 years and the standard deviation is 1.89 years. Construct a 96 percent confidence interval for the mean time required for all graduates to earn a bachelor's degree. 14. Suppose the college in question 13 has only graduated 10,000 students. Construct a 96 percent confidence interval for the mean time required for all graduates to earn a bachelor's degree. 15. Of a random sample of 90 firms with employee stock ownership plans, 50 indicated that the primary reason for setting up the plan was tax related. Develop a 90 percent confidence interval for the population proportion of