Exam 9: Estimation and Confidence Intervals

Suppose 1,600 of 2,000 registered voters sampled said they planned to vote for the Republican candidate for president. Using the 0.95 degree of confidence,what is the interval estimate for the population proportion (to the nearest 10th of a percent)?

If 95% and 98% confidence intervals were developed to estimate the true cost of an MP3 player with a known population standard deviation,what differences would they have?

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 99% level of confidence,what is the confidence interval for the proportion of students supporting the fee increase?

A point estimate is a single value used to estimate a population parameter.

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

A sample of 50 is selected from a known population of 250 elements. The population standard deviation is 15. Using the finite correction factor,what is the standard error of the sample means?

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?

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

A group of statistics students decided to conduct a survey at their university to estimate the average (mean)amount of time students spent studying per week. They sampled 554 students and found a mean of 22.3 hours per week. Assuming a population standard deviation of six hours,what is the 95% level of confidence?

Local government officials are interested in knowing if taxpayers are willing to support a school bond initiative that will require an increase in property taxes. A random sample of 750 likely voters was taken. Four hundred fifty of those sampled favored the school bond initiative. The 95% confidence interval for the true proportion of voters favoring the initiative is ________.

The mean weight of trucks traveling on a particular section of I-475 is not known. A state highway inspector needs an estimate of the population mean. He selects and weighs a random sample of 49 trucks and finds the mean weight is 15.8 tons. The population standard deviation is 3.8 tons. What is the 95% confidence interval for the population mean?

A sample mean is the best point estimate of ________.

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?

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. A 95% confidence interval is constructed. What does the confidence interval mean?

The distribution of Student's t has ________.

Of the following characteristics,the t-distribution and z-distribution are the same in all but one. Which one is it?

The z-score or z-value corresponding to a 95.34% confidence interval is ________.