Exam 9: Estimation and Confidence Intervals

Which statement(s) is/are correct about the t distribution?

When estimating a population mean with a confidence interval, a smaller margin of error requires a _________ sample size.

What kind of distribution is the t distribution?

A survey of households in a small town showed that in 850 of 1,200 sampled households, at least one member attended a town meeting during the year. Using the 99% level of confidence, what is the confidence interval for the proportion of households represented at a town meeting?

A company wants to estimate next year's total revenue. Why is an interval estimate preferred to a point estimate?

A finite population correction factor is used to adjust the _________________.

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?

A survey of an urban university (population of 25,450) showed that 750 of 1,100 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?

When the population standard deviation is unknown, a __________ statistic is used to compute a confidence interval.

Making generalized statements about a population based on sample information is called _________________.

Assuming a normal population with a known population standard deviation, the z statistic for a 90% confidence interval would be ____.

A sample of 100 is selected from a known population of 350 elements. The population standard deviation is 15. Using the finite correction factor, what is the standard error of the sample means?

A population has a known standard deviation of 25. A simple random sample of 49 items is taken from the selected population. The sample mean (x-bar) is 300. What is the margin of error at the 95% confidence level?

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. What is the 98% confidence interval to estimate the true cost of a gallon of milk?

When deciding on the number of observations to include in a sample, what would favor larger sample sizes?

To determine the size of a sample, the standard deviation of the population must be estimated by either taking a pilot survey or by approximating it based on knowledge of the population.

In relative terms, a _______ confidence level leads to a narrower confidence interval.

The distribution of Student's t has _________.

A population has a standard deviation of 25. We want to estimate the population mean within 2, with a 95% level of confidence. How large a sample is required?

Mileage tests were conducted on a randomly selected sample of 100 newly developed automobile tires. The results showed that the mean tread life was 50,000 miles, with a standard deviation of 3,500 miles. What is the best estimate of the mean tread life in miles for the entire population of these tires?