1) A random sample of the number of hours worked by 40 employeeshas a mean of 29.6 hours worked. Assume the population standarddeviation is 7.9 hours.
a. Using a 95% confidence level, find the margin of error, E,for the mean number of hours worked.
2) In a study of 265 subjects, the average score on theexamination was 63.8. Assume σ = 3.08.
a. What is a 95% confidence interval for ?
3) A college admissions director wishes to estimate the mean ageof all students currently enrolled. In a random sample of 20students, the mean age is found to be 22.9 years. From paststudies, the standard deviation is known to be 1.5 years, and thepopulation is normally distributed.
a. Construct a 90% confidence interval of the population meanage.
4) The weight of a product is measured in pounds. A sample of 50units is taken from a batch. The sample yielded the followingresults: = 75 lbs., and σ = 10 lbs.
a. Calculate a 99% confidence interval for .
