Exam 9: Estimation and Confidence Intervals

A survey of an urban university (population of 25,450) showed that 750 of 1100 students sampled attended a home football game during the season. Using the 90% level of confidence, what is the confidence interval for the proportion of students attending a football game?

There are 250 computer programmers employed at Computers.com, Inc. A sample of 50 programmers revealed that 30 graduated with a four-year college degree. Construct the 95 percent confidence interval for the proportion of all programmers who graduated from a four-year university.

An interval estimate is a single value used to estimate a population parameter.

To compute a confidence interval for a population proportion, a __________ is used.

When we use a confidence interval to reach a conclusion about the population mean, we are applying a type of reasoning or logic called

A sample of 100 students is selected from a known population of 1000 students to construct a 95% confidence interval for the average SAT score. What correction factor should be used to compute the standard error?

The test statistic for a problem involving any sample size and an unknown population standard deviation is the z distribution.

A local grocery store wants to estimate the mean daily number of gallons of milk sold to customers. Assume the number of gallons sold follows the normal distribution with a population standard deviation of 5.10 gallons. A random sample of 60 days shows that the mean daily number of gallons sold is 10.00. Compute a 99 percent confidence interval for the population mean.

A survey of 50 retail stores revealed that the average price of a microwave was $375 with a standard error of $20. Assuming the population is normally distributed, what is the 95% confidence interval to estimate the true cost of the microwave?

Increasing sample size provides a more _______________ interval estimate of a population parameter.

The Nile Superstore is conducting a survey of consumer preferences for a new wireless, e-book reader. A sample of 160 people reveals that 120 would buy the new reader. What is the 99 percent confidence interval for the population proportion?

Which of the following is NOT necessary to determine how large a sample to select from a population?

A survey of an urban university (population of 25,450) showed that 750 of 1100 students sampled attended a home football game during the season. Using the 99% level of confidence, what is the confidence interval for the proportion of students attending a football game?

What is the probability that an interval estimate includes the population parameter? _____________________

A sample mean is a _______________ of the population mean.

A local company wants to evaluate their quality of service by surveying their customers. Their budget limits the number of surveys to 100. What is their maximum error of the estimated mean quality for a 95% level of confidence and an estimated standard deviation of 5?

Recently, a university surveyed recent graduates of the English Department for their starting salaries. Four hundred graduates returned the survey. The average salary was $25,000. The population standard deviation is $2,500. What is the 95% confidence interval for the mean salary of all graduates from the English Department?

The estimate of the population proportion is to be within plus or minus .10, with a 95 percent level of confidence. The best estimate of the population proportion is .25. How large a sample is required?

A survey of 25 grocery stores revealed that the average price of a gallon of milk was $2.98 with a standard error of $0.10. If 90% and 95% confidence intervals are developed to estimate the true cost of a gallon of milk, what similarities would they have?

In terms of the standard error of the mean, how wide is a 99 percent confidence interval? ______