Exam 7: Sampling and Sampling Distributions

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

Catherine Chao,Director of Marketing Research,needs a sample of households to participate in the testing of a new toothpaste package.She directs the seven members of her staff to find five households each.Catherine's sample is a ___.

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

Suppose 40% of all seniors have a computer at home and a sample of 64 is taken.What is the probability that more than 30 of those in the sample have a computer at home?

Nonsampling error occurs when,due to chance,the sample is not representative of the population.

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 have a mean length of 120 centimetres and a standard deviation of 0.05 centimetres,the probability that Claude's sample has a mean less than 119.985 centimetres is ___.

Abel Alonzo,Director of Human Resources,is exploring employee absenteeism at the Harrison Haulers Plant.Abel knows that absenteeism varies significantly between departments.For example,workers in the wood shop are absent more than those in the tuning department and the size of the departments ranges from 40 to 120 workers.He orders a random sample of 10 workers from each of the six departments.Abel' sample is a ___.

Suppose 40% of the population possess a given characteristic.If a random sample of size 300 is drawn from the population,then the probability that 44% or fewer of the samples possess the characteristic is ___.

Pinky Bauer,Chief Financial Officer of Harrison Haulers,Inc. ,suspects irregularities in the payroll system.If 10% of the 5,000 payroll vouchers issued since January 1,2000,have irregularities,the probability that Pinky's random sample of 200 vouchers will have a sample proportion greater than .06 is ___.

According to the central limit theorem,if a sample of size 100 is drawn from a population with a standard deviation of 80,the standard deviation of sample means would equal ___.

On Saturdays,cars arrive at David Zebda's Scrub and Shine Car Wash at the rate of 80 cars per hour during the ten-hour shift.David wants a sample of 40 Saturday customers to answer the long version of his quality service questionnaire.He instructs the Saturday crew to select the first 40 customers.His sample is a ___.

Suppose a population has a mean of 870 and a variance of 8,100.If a random sample is size 36 is drawn from the population,the probability that the sample mean is between 840 and 900 is ___.

In a random sampling technique every unit of the population has a randomly varying chance or probability of being included in the sample.

Kristen Ashford purchased the subscribers list for Wind Surfing magazine.She plans to survey a sample of the subscribers before using the list in her mail order business.She chooses the first 100 of the 5,000 names.Her sample is a ___.

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 less than 16 minutes is ___.

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

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

Kristen Ashford purchased the subscribers list for Wind Surfing magazine.She plans to survey a sample of the subscribers before using the list in her mail order business.The names are numbered consecutively from 1 to 5,000.Kristen chooses her sample by selecting four-digit numbers (1 to 5,000)from a random number table.Her sample is a ___.

Suppose 40% of all seniors 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?

If a researcher selects every k^th item from a population of N items,then she is likely conducting a stratified random sampling.