Exam 9: Estimation and Confidence Intervals

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 3 hours,what is the required sample size if the error should be less than ½ hour with a 99% level of confidence?

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

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 6 hours,what is the required sample size if the error should be less than ½ hour with a 95% level of confidence?

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?

The population variation as measured by the standard deviation has little or no effect in determining the size of a sample selected from the population.

A random sample of 85 group leaders and 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?

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?

There are 2,000 eligible voters in a precinct.500 of the voters are randomly selected and asked whether they planned to vote for the Democratic incumbent or the Republican challenger.Of the 500 surveyed,350 said they would vote for the Democratic incumbent.Using the 0.99 confidence coefficient,what are the confidence limits for the proportion that plan to vote for the Democratic incumbent?

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.

A sample of 25 is selected from a known population of 100 elements.What is the finite population correction factor?

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.They sampled 240 students and found a mean of 22.3 hours per week.Assuming a population standard deviation of 6 hours,what is the 99% level of confidence?

A sample of 2000 union members was selected and their opinions regarding a proposed management union contract were recorded.1,600 members were in favor of it.A 95% confidence interval for the population proportion was computed to be 0.78 and 0.82.This indicates that about 80 out of 100 similarly constructed intervals would include the population proportion.

What type of estimate states the range within which a population parameter probably lies? _____________

The test statistic t has n - 1 degrees of freedom.

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?

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 99% confidence interval to estimate the true cost of the microwave?

Which of the following would be used as a point estimate for the population mean ( µ )?

Assuming a population standard deviation of 3 hours,what is the required sample size if the error should be less than ½ hour with a 99% level of confidence?

The t distribution is positively skewed.

There is not one t distribution,but rather a "family" of t distributions.