Exam 9: Estimation and Confidence Intervals

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,with a standard deviation of $2,500. What is the best point estimate of the population mean?

A survey of 25 grocery stores revealed that the mean price of a gallon of milk was $2.98,with a standard error of $0.10. What is the 95% confidence interval to estimate the true cost of a gallon of milk?

To determine the value of the standard error of the mean,the standard deviation is divided by the sample size.

What is the interpretation of a 96% confidence level?

One factor in determining the size of a sample is the degree of confidence selected. This is usually 0.95 or 0.99,but it may be any degree of confidence you specify.

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?

A random sample of 85 supervisors revealed that they worked an average of 6.5 years before being promoted. The population standard deviation was 1.7 years. Using the 0.95 degree of confidence,what is the confidence interval for the population mean?

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 1,000 students to construct a 95% confidence interval for the average SAT score. What correction factor should be used to compute the standard error?

A survey of an urban university (population of 25,450)showed that 870 of 1,100 students sampled supported a fee increase to fund improvements to the student recreation center. Using the 95% level of confidence,what is the confidence interval for the proportion of students supporting the fee increase?

A point estimate is a range of values used to estimate a population parameter.

A student wanted to construct a 95% confidence interval for the mean age of students in her statistics class. She randomly selected nine students. Their average age was 19.1 years with a sample standard deviation of 1.5 years. What is the best point estimate for the population mean?

The population variation has little or no effect in determining the size of a sample selected from the population.

A sample of 2,000 union members was selected,and a survey recorded their opinions regarding a proposed management union contract. A total of 1,600 members were in favor of it. A 95% confidence interval estimated that the population proportion was between 0.78 and 0.82. This indicates that about 80 out of 100 similarly constructed intervals would include the population proportion.

The distribution of Student's t is ________.

An interval estimate is a range of values in which the population parameter is likely to occur.

A group of statistics students decided to conduct a survey at their university to find the average (mean)amount of time students spent studying per week. Assuming a population standard deviation of six hours,what is the required sample size if the error should be less than a half hour with a 95% level of confidence?

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 was $2,500. What is the 95% confidence interval for the mean salary of all graduates from the English department?

A survey of 50 retail stores revealed that the average price of a microwave was $375,with a sample standard deviation of $20. If 90% and 95% confidence intervals were developed to estimate the true cost of the microwave,what similarities would they have?

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?