Exam 7: Sampling and Sampling Distributions

Sampling errors cannot by determined objectively for nonrandom sampling techniques.

Suppose the population of all public Universities shows the annual parking fee per student is $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 _______.

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 randomly selects 9 as a starting point and instructs the crew to select the 9th customer and each customer at intervals of 20 (9,29,49,etc.). His sample is a __________.

The sampling distribution of has a mean equal to the square root of the population proportion p.

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 randomly selects 53 as a starting point and orders her staff to inspect the 53rd voucher and each voucher at an increment of 100 (53,153,253,etc.). 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 15 minutes is ________.

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 _____________.

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

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 uses random five-digits numbers from the website random.org (which offers true random numbers on the Internet).This is an example of ______.

Saving time and money are reasons to take a sample rather than do a census.

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 ___________.

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

Suppose 40% of all college students 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?

In Norway,approximately 22% of vehicles are electric vehicles.What is the probability of randomly selecting 250 cars and finding out that 60 or more are electric?

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 _______.

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 standard deviation of the sample means would be ______.

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

Suppose 30% of the U.S.population has green eyes.If a random sample of size 1200 U.S.citizens is drawn,then the probability that less than 348 U.S.citizens have green eyes is _______.

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?

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