Stats chapter 7 practice exam

Sampling distributions describe the distribution of a) parameters. b) statistics. c) both parameters and statistics. d) neither parameters nor statistics.

b) statistics

The mean of the sampling distribution of a sample proportion is the population proportion, π. true or false

true

According to a survey, only 15% of customers who visited the web site of a major retail store made a purchase. Random samples of size 50 are selected. Referring to the above scenario, the standard deviation of all the sample proportions of customers who will make a purchase after visiting the web site is ________.

0.05050

According to a survey, only 15% of customers who visited the web site of a major retail store made a purchase. Random samples of size 50 are selected. Referring to the above scenario, the mean of all the sample proportions of customers who will make a purchase after visiting the web site is ________.

0.15 15%

According to a survey, only 15% of customers who visited the web site of a major retail store made a purchase. Random samples of size 50 are selected. Referring to the above scenario, what proportion of the samples will have between 20% and 30% of customers who will make a purchase after visiting the web site?

0.1596

The amount of bleach a machine pours into bottles has a mean of 36 oz. with a standard deviation of 0.15 oz. Suppose we take a random sample of 36 bottles filled by this machine. The probability that the mean of the sample exceeds 36.01 oz. is

0.3446

According to a survey, only 15% of customers who visited the web site of a major retail store made a purchase. Random samples of size 50 are selected. Referring to the above scenario, what proportion of the samples will have less than 15% of customers who will make a purchase after visiting the web site?

0.5

The amount of bleach a machine pours into bottles has a mean of 36 oz. with a standard deviation of 0.15 oz. Suppose we take a random sample of 36 bottles filled by this machine. The probability that the mean of the sample is between 35.94 and 36.06 oz. is ________.

0.9836

The owner of a fish market has an assistant who has determined that the weights of catfish are normally distributed, with mean of 3.2 pounds and standard deviation of 0.8 pound. If a sample of 64 fish yields a mean of 3.4 pounds, what is probability of obtaining a sample mean this large or larger? a) 0.0228 b) 0.0001 c) 0.0013 d) 0.4987

a) 0.0228

The owner of a fish market has an assistant who has determined that the weights of catfish are normally distributed, with mean of 3.2 pounds and standard deviation of 0.8 pound. If a sample of 16 fish is taken, what would the standard error of the mean weight equal? a) 0.200 b) 0.050 c) 0.003 d) 0.800

a) 0.200

Which of the following is true regarding the sampling distribution of the mean for a large sample size? a) It has a normal distribution with the same mean as the population but with a smaller standard deviation. b) It has a normal distribution with the same mean and standard deviation as the population. c) It has the same shape and mean as the population, but has a smaller standard deviation. d) It has the same shape, mean, and standard deviation as the population

a) It has a normal distribution with the same mean as the population but with a smaller standard deviation.

Which of the following is NOT a reason for the need for sampling? a) It is always more informative by investigating a sample than the entire population b) It is sometimes destructive to observe the entire population. c) It is usually too costly to study the whole population. d) It is usually too time consuming to look at the whole population

a) It is always more informative by investigating a sample than the entire population

The owner of a fish market has an assistant who has determined that the weights of catfish are normally distributed, with mean of 3.2 pounds and standard deviation of 0.8 pound. If a sample of 25 fish yields a mean of 3.6 pounds, what is the Z-score for this observation? a) 1.875 b) 2.500 c) 0.750 d) 18.750

b) 2.500

Which of the following yields a stratified sample? a) The first 15 students in a class are selected without replacement. b) All students in a class are grouped according to their gender. A random sample of 8 is selected from the males and a separate random sample of 7 is drawn from the females. c) All students in a class are divided into groups of 15. One student is randomly chosen from the first group, the remaining observations are every 15th student thereafter. d) The best 15 students, according to the opinion of the instructor, in a class are selected.

b) All students in a class are grouped according to their gender. A random sample of 8 is selected from the males and a separate random sample of 7 is drawn from the females.

Which of the following yields a systematic sample? a) All students in a class are grouped according to their gender. A random sample of 8 is selected from the males and a separate random sample of 7 is drawn from the females. b) A random sample of 15 students is selected from a class without replacement. c) All students in a class are divided into groups of 15. One student is randomly chosen from the first group, the remaining observations are every 15th student thereafter. d) The best 15 students, according to the opinion of the instructor, in a class are selected.

c) All students in a class are divided into groups of 15. One student is randomly chosen from the first group, the remaining observations are every 15th student thereafter.

Which of the following is true about the sampling distribution of the sample mean? a) The standard deviation of the sampling distribution is always σ. b) The shape of the sampling distribution is always approximately normal. c) The mean of the sampling distribution is always μ. d) All of the above are true.

c) The mean of the sampling distribution is always μ.

Which of the following yields a simple random sample? a) All students in a class are divided into groups according to the rows in which they are seated. One of the groups is randomly selected. b) All students in a class are divided into groups of 15. One student is randomly chosen from the first group, the remaining observations are every 15th student thereafter. c) The names of 50 students in a class are written on 50 different pieces of paper and put in a hat. The first 15 pieces of paper are selected blindly one at a time without replacing them back in the hat after shuffling the papers thoroughly. d) The best 15 students, according to the opinion of the instructor, in a class are selected.

c) The names of 50 students in a class are written on 50 different pieces of paper and put in a hat. The first 15 pieces of paper are selected blindly one at a time without replacing them back in the hat after shuffling the papers thoroughly.

To obtain a sample of 10 books in the store, the manager walked to the first shelf next to the cash register to pick the first 10 books on that shelf. This is an example of a a) stratified sample. b) simple random sample. c) convenience sample. d) systematic sample

c) convenience sample

The Central Limit Theorem is important in statistics because a) for a large n, it says the population is approximately normal. b) for a sample of any size, it says the sampling distribution of the sample mean is approximately normal. c) for a large n, it says the sampling distribution of the sample mean is approximately normal, regardless of the shape of the population. d) for any population, it says the sampling distribution of the sample mean is approximately normal, regardless of the sample size.

c) for a large n, it says the sampling distribution of the sample mean is approximately normal, regardless of the shape of the population.

Which of the following yields a cluster sample? a) All students in a class are divided into groups of 15. One student is randomly chosen from the first group, the remaining observations are every 15th student thereafter. b) All students in a class are grouped according to their gender. A random sample of 8 is selected from the males and a separate random sample of 7 is selected from the females. c) The best 15 students, according to the opinion of the instructor, in a class are selected. d) All students in a class are divided into groups according to the rows in which they are seated. One of the groups is randomly selected.

d) All students in a class are divided into groups according to the rows in which they are seated. One of the groups is randomly selected.

The standard error of the mean a) decreases as the sample size increases. b) is never larger than the standard deviation of the population. c) measures the variability of the mean from sample to sample. d) all of the above

d) all of the above

At U.S. Data Corporation's web site, they advertised that "Because of our commitment to quality and our vast amount of industry knowledge and experience, we have grown to be one of America's leading providers of mailing lists, marketing data, sales leads and research data. We maintain databases of information on consumers and businesses nationwide that set industry standards for mission critical currency, reliability, and accuracy." Trying to reach 500 potential donors for their annual phone donation campaign, a local fire department purchased a list of donors from the company. This list is an example of a a) statistic. b) population. c) parameter. d) frame.

d) frame

Sampling error can be completely eliminated by taking larger sample sizes. true or false

false

The difference between the sample proportion and the population proportion is called the sampling error. true or false

false

The standard error of the sampling distribution of a sample proportion is the square root of (p(1-p)) / n), where p is the sample proportion. true or false

false

For a given data set, the confidence interval will be wider for 95% confidence than for 90% confidence. true or false

true

If a simple random sample is chosen with replacement, each individual has the same chance of selection on every selection. true or false

true

If the population distribution is unknown, in most cases the sampling distribution of the mean can be approximated by the normal distribution if the samples contain at least 30 observations. true or false

true