You want to purchase one of the new Altima. You randomly select 400 dealerships across the United States and find a mean of $25,000. Assume a population standard deviation of $2500. Construct and interpret a 94% confidence interval for the true mean price for the new Nissan Altima.

A company wants to estimate the average time employees spend on a training module. 15 employees are randomly selected, & their completion times recorded. The sample of times to complete the module is normally distributed with mean 42.7 min & std. dev. 5.4 min.

(B) Should management be concerned that the training might take too long if their policy states the module should take at most 45 min? Justify your answer using your confidence interval.

A beverage company claims that on average, customers consume 500 mL of their new energy drink in a single sitting. To test this claim, a market researcher collects a random sample of 8 customers. Assume the sample is normal & make a 90% conf. int. for the true mean volume. Does the data support the company’s claim?

A retailer wants to estimate the average amount spent by customers on holiday shopping. In a random sample of 50 customers, the average amount spent was $250, and the population standard deviation $\sigma$ is known to be $40. Construct and interpret an 80% confidence interval for the average amount spent by all customers.

Books get more and more expensive every semester, but the distribution of their prices is always normal. 25 randomly selected students in your school spent, on average $500 with a standard deviation of $50. Construct a 98% confidence interval for the true spending on books.

Find the critical value $t_{\frac{\alpha}{2}}$for an 80% confidence interval given a sample size of 51.

Find the critical value $t_{\frac{\alpha}{2}}$for a 95% confidence interval given a sample size of 6.

For which of the following scenarios can you NOT create a confidence interval using the standard normal or Student t-distribution?

You ask 16 people in your Statistics class what their grade is. The data appears to be distributed normally. You find a sample mean and sample standard deviation of 60 and 24, respectively. Construct and interpret a 95% confidence interval for the population mean class grade.