Exam 7: Sampling and Sampling Distributions

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 closest to___.

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?

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?

In some situations sampling may be the only option because the population is inaccessible.

A sampling distribution is the distribution of a sample statistic such as the sample mean or sample proportion.

When determining the value of k the correct calculation is n/N.

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 ___.

The standard deviation of the sample means is commonly called the standard error of the mean.

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 ___.

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

If the population proportion is 0.90 and a sample of size 64 is taken, what is the probability that the sample proportion is more than 0.89?

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?

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 of between .06 and .14 is closest to___.

If the population is normally distributed, the sample means of size n=5 are normally distributed.

Suppose a population has a mean of 90 and a standard deviation of 28.If a random sample of size 49 is drawn from the population, the probability of drawing a sample with a mean of less than 84 is ___.

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 15 minutes is ___.

According to the central limit theorem, for samples of size 169 drawn from a population with µ = 1,014 and σ = 65, the mean of the sample means would equal ___.

Suppose a population has a mean of 90 and a standard deviation of 28.If a random sample of size 49 is drawn from the population, the probability of drawing a sample with a mean between 80 and 100 is ___.

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 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 of more than 404.5 is ___.