Exam 7: Sampling and Sampling Distributions

Albert Abbasi,VP of Operations at Ingleside International Bank,is evaluating the service level provided to walk-in customers.Accordingly,he plans a sample of waiting times for walk-in customers.If the population of waiting times has a mean of 15 minutes and a standard deviation of 4 minutes,the probability that Albert's sample of 64 will have a mean between 13.5 and 16.5 minutes is ________.

Suppose 40% of all college students have a computer at home and a sample of 100 is taken.What is the probability that more than 50 of those in the sample have a computer at home?

Suppose 40% of the population of pre-teens have a TV in their bedroom.If a random sample of 500 pre-teens is drawn from the population,then the probability that 44% or fewer of the pre-teens have a TV in their bedroom is _______.

Paige DeMarco is the Vice President for University Advancement at State University.She is responsible for the capital campaign to raise money for the new student services building.Paige plans to target alumni and acquires her sampling frame from the State University Office of Alumni Relations.She intends to contact these individuals regarding possible donations.She randomly selects the sixth name as a starting point and then selects every 100th subsequent name (106,206,306,etc.).Her sample is a _________.

If the population proportion is 0.90 and a sample of size 64 is taken,what is the probability that the sample proportion is less than 0.88?

Pinky Bauer,Chief Financial Officer of Harrison Haulers,Inc.,suspects irregularities in the payroll system.She knows that 2,500 payroll vouchers have been issued since January 1,2000,and her staff doesn't have time to inspect each voucher.So,she orders her staff to inspect the last 200 vouchers.Her sample is a ___________.

Catherine Chao,Director of Marketing Research,needs a sample of Kansas City households to participate in the testing of a new toothpaste package.If 40% of the households in Kansas City prefer the new package,the probability that Catherine's random sample of 300 households will have a sample proportion greater than 0.45 is ___________.

Decreasing the sample size causes the sampling distribution of to ________.

A carload of steel rods has arrived at Cybermatic Construction Company.The car contains 50,000 rods.Claude Ong,manager of Quality Assurance,directs his crew measure the lengths of 100 randomly selected rods.If the population of rods has a mean length of 120 inches and a standard deviation of 0.05 inch,the probability that Claude's sample has a mean greater than 120.0125 inches is _____________.

With cluster sampling,there is homogeneity within a subgroup or stratum.

A nonrandom sampling technique that is similar to stratified random sampling is called quota sampling.

Suppose 90% of students in some specific college have a computer at home and a sample of 40 students is taken.The probability that more than 30 of those in the sample have a computer at home can be approximated using the normal approximation.

Suppose 40% of the population of pre-teens have a TV in their bedroom.If a random sample of 500 pre-teens is drawn from the population,then the probability that 44% or more of the pre-teens have a TV in their bedroom is _______.

According to the central limit theorem,for samples of size 64 drawn from a population with  = 800 and  = 56,the standard deviation of the sampling distribution of sample means would equal _______.

Catherine Chao,Director of Marketing Research,needs a sample of households to participate in the testing of a new toothpaste package.She chooses thirty-six of her closest friends.Catherine's sample is a _____________.

If every unit of the population has the same probability of being selected to the sample,then the researcher is conducting random sampling.

Suppose a population has a mean of 870 and a variance of 1,600.If a random sample of size 64 is drawn from the population,the probability that the sample mean is between 860 and 875 is _______.

Suppose a population has a mean of 400 and a standard deviation of 24.If a random sample of size 144 is drawn from the population,the probability of drawing a sample with a mean less than 402 is _______.

Financial analyst Larry Potts needs a sample of 100 securities listed on the New York Stock Exchange.In the current issue of the Wall Street Journal,2,531 securities are listed in the "New York Exchange Composite Transactions," an alphabetical listing of all securities traded on the previous business day.Larry uses a table of random numbers to select 100 numbers between 1 and 2,531.His sample is a ____________.

Suppose 65% of all college students have a laptop computer at home and a sample of 150 students is taken.The mean of the sampling distribution of is