Question 1

To estimate the average annual expenses of students on books and class materials a sample of size 36 is taken. The mean is $850 and the standard deviation is $54. A 99% confidence interval for the population mean is

Question 2

A random sample of 16 ATM transactions at the Last National Bank of Flatrock revealed a mean transaction time of 2.8 minutes with a standard deviation of 1.2 minutes. The width (in minutes) of the 95% confidence interval for the true mean transaction time is

Question 3

A financial institution wishes to estimate the mean balances owed by its credit card customers. The population standard deviation is estimated to be $300. If a 99 percent confidence interval is used and an interval of ±$75 is desired, how many cardholders should be sampled?

Question 4

Oxnard Beneficial Insurance wants to estimate the cost of damage to cars due to accidents. The standard deviation of the cost is estimated at $200. They want to estimate the mean cost using a 95% confidence interval within ± $10. What is the minimum sample size n?

Question 5

We could narrow a 95% confidence interval by

Question 6

Jolly Blue Giant Health Insurance (JBGHI) is concerned about rising lab test costs and would like to know what proportion of the positive lab tests for prostate cancer are actually proven correct through subsequent biopsy. JBGHI demands a sample large enough to ensure an error of ± 2% with 90% confidence. What is the necessary sample size, to be conservative?

Question 7

If a normal population has parameters μ= 40 and σ= 8, then for a sample size n = 4

Question 8

The sample proportion lies within the confidence interval for the population proportion.

Question 9

An airport traffic analyst wants to estimate the proportion of daily takeoffs by small business jets (as opposed to commercial passenger jets) with an error of ±4 percent with 90 percent confidence. What sample size should the analyst use?

Question 10

Use the conventional polling definition, find the margin of error for a customer satisfaction survey of 225 customers who have recently dined at Applebee's.