A savings and loan association needs information concerning the checking account balances of its local customers. A random sample of 15 accounts was checked and yielded a mean balance of $664.14 and a standard deviation of $297.29. Find a 95% confidence interval for the true mean checking account balance for local customers

Scientists want to estimate the mean weight gain of mice after they have been fed a special diet. From previous studies, it is known that the weight gain is normally distributed with standard deviation 3.5 grams. How many mice must be weighed so that a 90% confidence interval for mean weight will have a margin of error of 0.4 grams?

A group of 69 randomly selected students have a mean score of 24.1 with a population standard deviation of 5.0 on a placement test. What is the 90% confidence interval for the mean score, μ, of all students taking the test?

An Internet service provider sampled 570 customers and found that 60 of them experienced an interruption in their service during the previous month. Construct a 98% confidence interval for the proportion of all customers who have experienced a service interruption.

A researcher wants to construct a 98% confidence interval for the proportion of elementary school students in Seward County who receive free or reduced-price school lunches. A state-wide survey indicates that the proportion is 0.60. Using this estimate, what sample size is needed so that the confidence interval will have a margin of error of 0.07?

Measurements were made of the milk fat content (in percent) in six brands of feta cheese (a variety of goat cheese), with the following results. Assume that the population is normally distributed. 16.7 20.1 19.6 21.7 22.0 23.9 Construct a 90% confidence interval for the population standard deviation σ.