Exam 8: Interval Estimation

In 2015, approximately 136,943,000 people visited an emergency room in the United States.Of these, approximately 12,263,000 were subsequently admitted to the hospital.Determine an interval with 99% confidence for the number (how many) of people visiting an emergency room who were subsequently admitted to the hospital.

A random sample of 25 employees of a local company has been taken.A 95% confidence interval estimate for the mean systolic blood pressure for all employees of the company is 123 to 139.Which of the following statements is valid?

In an interval estimation for a proportion of a population, the value of z at 99.2% confidence is

In a random sample of 100 observations, = .2.The 95% confidence interval for p is

We are interested in conducting a study to determine the percentage of voters of a state would vote for the incumbent governor.What is the minimum sample size needed to estimate the population proportion with a margin of error of .05 or less at 95% confidence?

In general, higher confidence levels provide

A sample of 123,456 Amazon Prime members were selected, and it was determined that 87,654 had made a purchase sometime from Thanksgiving to Cyber Monday.Develop a 95% confidence interval for the population proportion.

In a sample of 200 individuals, 130 indicated they are Democrats.Develop a 95% confidence interval for the proportion of Democrats in the population.

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

A random sample of 95 students at a local university showed that they work an average of 48 hours per month with a standard deviation of 12 hours.Compute a 95% confidence interval for the mean of the population.

The monthly starting salaries of students who receive an MBA degree have a population standard deviation of $110.What sample size should be selected to obtain a .95 probability of estimating the population mean monthly income within a margin of $20?

An Excel printout of the descriptive measures of a sample 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 account balances.

From a population that is normally distributed, a sample of 25 elements is selected and the standard deviation of the sample is computed.For the interval estimation of μ, the proper distribution to use is the

A random sample of 144 checking accounts at a bank showed an average daily balance of $500 and a standard deviation of $60.Develop a 95% confidence interval estimate for the mean of the population.

If the population standard deviation of the lifetime of washing machines is estimated to be 1000 hours, how large a sample must be taken in order to be 95% confident that the margin of error will not exceed 100 hours?

In order to estimate the proportion of individuals who read at least one book per month, a random sample of individuals at a book fair was selected and they were asked whether or not they read at least one book per month.Their responses are shown below. ​ Develop a 95% confidence interval for the proportion of individuals in the population who read at least one book per month.

A random sample of 64 students at a university showed an average age of 25 years and a sample standard deviation of 2 years.The 95% confidence interval for the true average age of all students in the university is

A random sample of 25,000 ACT test takers had an average score of 21 with a standard deviation of 5.Determine the standard error.

We can reduce the margin of error in an interval estimate of p by doing any of the following except​

In developing an interval estimate, if the population standard deviation is unknown,