Exam 7: Sampling and Sampling Distributions

The employees in certain division of Cybertronics Inc.need to complete a certification online.On average, it takes 20 hours to complete the coursework and successfully pass all tests, with a standard deviation of 6 hours.If you select a random sample of size 30, the probability that the employees in your sample have taken, on average, more than 20.5 hours is ______.

Suppose the population of all public Universities shows the annual parking fee per student is normally distributed with a mean of $110 with a standard deviation of $18.If a random sample of size 49 is drawn from the population, the probability of drawing a sample with a mean of more than $115 is closest to _______.

Suppose the population of all public Universities shows the annual parking fee per student is normally distributed with a mean of $110 with a standard deviation of $18.If a random sample of size 49 is drawn from the population, the probability of drawing a sample with a sample mean between $112 and $115 is closest to _______.

A major limitation of nonrandom samples is that they are not appropriate for most statistical methods.

The sampling distribution of the sample means is less variable than the population distribution.

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

If random variable X is distributed according to a uniform distribution between 0 and 1 (X ~ U[0, 1]), and 100 random samples of sizes 35-40 were taken, the sum of the sample means would be ______.

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

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 _____________.

Certain transportation company has a fleet of 210 vehicles.The average age of the vehicles is 4.25 years, with a standard deviation of 18 months.In a random sample of 40 vehicles, what is the probability that the average age of vehicles in the sample will be less than 4 years?

Suppose the population of all public Universities shows the annual parking fee per student is normally distributed with a mean of $110 with a standard deviation of $18.If a random sample of size 49 is drawn from the population, the probability of drawing a sample with a mean of less than $92 is closest to _______.

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, 2018, have irregularities, the probability that Pinky's random sample of 200 vouchers will have a sample proportion greater than .06 is closest to ___________.

According to the central limit theorem, if a sample of size 64 is drawn from a population with a standard deviation of 80, the standard deviation of sample means would equal _______.

Alice Zhong is the VP of Operations at Pearl Financial Services.She wants to measure customer satisfaction after a new website and other changes were introduced a few months ago.For this purpose, she instructs her staff to prepare a questionnaire and send it to the first 200 clients in their alphabetical list of active clients.This is an example of ______.

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

A random sample of size 100 is drawn from a population with a standard deviation of 10.If only 5% of the time a sample mean greater than 20 is obtained, the mean of the population is closest to ______

According to the central limit theorem, if a sample of size 100 is drawn from a population with a mean of 80, the mean of all sample means would equal _______.

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.Albert instructs his staff to record the waiting times for the first 45 walk-in customers arriving after the noon hour.Albert's sample is a ________.

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 to measure the lengths of 100 randomly selected rods.If the population of rods have a mean length of 120 inches and a standard deviation of 0.05 inch, the probability that Claude's sample has a mean less than 119.985 inches is closest to _____________.

A population list, map, directory, or other source used to represent the population and from which a sample is taken, is called a frame.