Exam 8: Interval Estimation

A random sample of 121 checking accounts at a bank showed an average daily balance of $300 and a standard deviation of $44.Develop a 95% confidence interval estimate for the mean of the population.

In a random sample of 144 observations, = 0)6.The 95% confidence interval for P is

In order to determine the summer unemployment rate among college students,a pilot sample was taken;and it was determined that ten percent of the individuals in the sample were unemployed.Using the results of the pilot study and a 95% confidence,what size sample would be required to estimate the proportion of unemployed college students if we want the margin of error not to exceed 3 percent?

A university planner is interested in determining the percentage of spring semester students who will attend summer school.She takes a pilot sample of 160 spring semester students discovering that 56 will return to summer school. a.Construct a 95% confidence interval estimate for the percentage of spring semester students who will return to summer school. b.Using the results of the pilot study with a 0.95 probability,how large of a sample would have to be taken to provide a margin of error of 3% or less?

From a population that is not normally distributed and whose standard deviation is not known,a sample of 6 items is selected to develop an interval estimate for the mean of the population ( $\mu$ ).

We are interested in conducting a study in order to determine what percentage of voters of a state would vote for the incumbent governor.What is the minimum size sample needed to estimate the population proportion with a margin of error of 0.05 or less at 95% confidence?

The following random sample from a population whose values were normally distributed was collected. The 80% confidence interval for $\mu$ is

A 95% confidence interval for a population mean is determined to be 100 to 120.If the confidence coefficient is reduced to 0.90,the interval for $\mu$

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. a.Is it necessary to know anything about the shape of the distribution of the account balances in order to make an interval estimate of the mean of all the account balances? Explain. b.Find the standard error of the mean. c.Give a point estimate of the population mean. d.Construct a 80% confidence interval estimates for the mean. e.Construct a 95% confidence interval for the mean.

An Excel printout of the descriptive measures of daily checking account balances (in dollars)of customers of First Daisy Bank is shown below.Develop a 95% confidence interval estimate for the mean of the population of the checking balances.

The proprietor of a boutique in New York wanted to determine the average age of his customers.A random sample of 53 customers revealed an average age of 28 years with a standard deviation of 4 years.Determine a 98% confidence interval estimate for the average age of all his customers.