Exam 8: Estimating Single Population Parameters

Suppose that an internal report submitted to the managers at a bank in Boston showed that with 95 percent confidence,the proportion of the bank's customers who also have accounts at one or more other banks is between .45 and .51.Given this information,what sample size was used to arrive at this estimate?

If a pilot sample of n = 40 items has been used as a first step in determining a required sample size of n = 360,the decision maker can go ahead and use these 40 and take a sample of only 320 more items.

When using a 95 percent confidence interval for a mean,the area in the upper tail of the distribution that is outside the interval is 5 percent.

Allante Pizza delivers pizzas throughout its local market area at no charge to the customer.However,customers often tip the driver.The owner is interested in estimating the mean tip income per delivery.To do this,she has selected a simple random sample of 12 deliveries and has recorded the tips that were received by the drivers.These data are: Suppose the owner is interested in developing a 90% confidence interval estimate.Given the fact that the population standard deviation is unknown,what distribution will be used to obtain the critical value?

In determining the sample size requirement for an application involving the estimation of the proportion of department store customers who pay using the store's credit card,the closer the true proportion is to .5,the larger will be the required sample size for a given margin of error and confidence level.

Which of the following statements is true with respect to the confidence level associated with an estimation application?

The general format for a confidence interval is:

If a decision maker desires a small margin of error and a high level of confidence,it is certain that the required sample size will be quite large.

In estimating a population mean,a large sample size is generally preferable to a small sample size because the margin of error is generally smaller.

Twenty one (21)customers out of a simple random sample of 50 said that they came to the grocery store within one month after getting a card from the company.Based on the data,the marketing manager thinks that the number of total customers who would come in to the grocery store within one month is 4,200 because 10,000 cards were mailed.

One of the major oil products companies conducted a study recently to estimate the mean gallons of gasoline purchased by customers per visit to a gasoline station.To do this,a random sample of customers was selected with the following data being recorded that show the gallons of gasoline purchased. Based on these sample data,construct and interpret a 95 percent confidence interval estimate for the population mean.

A pilot sample of 75 items was taken,and the number of items with the attribute of interest was found to be 15.How many more items must be sampled to construct a 99% confidence interval estimate for p with a 0.025 margin of error?

A manager wishes to estimate a population mean using a 95% confidence interval estimate that has a margin of error of ±44.0.If the population standard deviation is thought to be 680,what is the required sample size?

Which of the following statements is true with respect to the t-distribution?

Sampling error occurs when:

A survey of 499 women for the American Orthopedic Foot and Ankle Society revealed that 38% wear flats to work. Suppose the society also wishes to estimate the proportion of women who wear athletic shoes to work with a margin of error of 0.01 with 95% confidence.Determine the sample size required.

Past experience indicates that the variance in the time it takes for a "fast lube" operation to actually complete the lube and oil change for customers is 9.00 minutes.The manager wishes to estimate the mean time with 99 percent confidence and a margin of error of ± 0.50 minutes.Given this,what must the sample size be?

The chamber of commerce in a beach resort town wants to estimate the proportion of visitors who are repeat visitors.Suppose that they have estimated that they need a sample size of n=16,577 people to achieve a margin of error of ± .01 percentage points with 99 percent confidence,but this is too large a sample size to be practical.How can they reduce the sample size?

The impact on the margin of error for a confidence interval for an increase in confidence level and a decrease in sample size is unknown since these changes are contradictory.

The following data represent a random sample of bank balances for a population of checking account customers at a large eastern bank.Based on these data,what is the 95 percent confidence interval estimate for the true population mean?