1. Choo Choo Paper Company produces papers of various thicknesses. A random sample of 49 cuts had a mean thickness of 30.3 mils with a sample standard deviation of 4 mils.
a) Develop a 99% confidence interval for the mean thickness of the population.
b) Develop a 90% confidence interval for the mean thickness of the population.
2. A random sample of 121 checking accounts at a bank showed an average daily balance of $280. The standard deviation of the population is known to be $66. Construct a 95% confidence interval estimates for the mean.
3. Using the mean, standard deviation and confidence level from the previous question, how large a sample size would you need to use to achieve a margin of error of 7 dollars?