Exam 9: Estimation and Confidence Intervals

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

Forty-nine items are randomly selected from a population of 200 items. The sample mean is 30 and the sample standard deviation 16. What is the 99 percent confidence interval for the population mean?

The proportion of junior executives leaving large manufacturing companies within three years is to be estimated within 3 percent. The 0.95 degree of confidence is to be used. A study conducted several years ago revealed that the percent of junior executives leaving within three years was 21. To update this study, the files of how many junior executives should be studied?

A student wanted to construct a 95% confidence interval for the average age of students in her statistics class. She randomly selected 9 students. Their average age was 19.1 years with a standard deviation of 1.5 years. What is the best point estimate for the population mean?

The mean number of travel days per year for salespeople employed by hardware distributors needs to be estimated with a 0.90 degree of confidence. For a small pilot study the mean was 150 days and the standard deviation was 14 days. If the population mean is estimated within two days, how many salespeople should be sampled?

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

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

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?

What is the interval within which a population parameter is expected to lie? __________________