Statistics a10

Assignment 10

1. A sample of 144 cans of coffee showed that an average weight of 16 ounces. The

standard deviation of the population is known to be 1.4 ounces.

a. Construct a 95% and 99% confidence interval for the mean of the population

b. Discuss why CI intervals are different in part a depending on the confidence level.

2. The monthly incomes from a random sample of workers in a factory are shown below. Be

aware that this is the standard deviation of the population unknown case.

Monthly Income

(In $)

4000

5000

7000

4000

6000

6000

7000

9000

a. Compute the point estimate of population mean and the point estimate of the

population standard deviation (in dollars)

b. Compute the margin of error (in dollars) at 95% confidence

c. Compute a 95% confidence interval for the mean of the population. Assume the

population has a normal distribution. Give your answer in dollars.