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    第一章 简介及数据收集(introduction and data collection)

    第一章测验题

    1、the process of using sample statistics to draw conclusions about true population parameters is called
        a、statistical inference.
        b、the scientific method.
        c、sampling.
        d、descriptive statistics.

    2、those methods involving the collection, presentation, and characterization of a set of data in order to properly describe the various features of that set of data are called
        a、statistical inference.
        b、the scientific method.
        c、sampling.
        d、descriptive statistics.

    3、the collection and summarization of the socioeconomic and physical characteristics of the employees of a particular firm is an example of
        a、inferential statistics.
        b、descriptive statistics.
        c、a parameter.
        d、a statistic.

    4、the estimation of the population average family expenditure on food based on the sample average expenditure of 1,000 families is an example of
        a、inferential statistics.
        b、descriptive statistics.
        c、a parameter.
        d、a statistic.

    5、the universe or "totality of items or things" under consideration is called
        a、a sample.
        b、a population.
        c、a parameter.
        d、a statistic.

    第二章 用图表展示数据(presenting data in tables and charts)

    第二章测验题

    1、an insurance company evaluates many numerical variables about a person before deciding on an appropriate rate for automobile insurance. a representative from a local insurance agency selected a random sample of insured drivers and recorded, x, the number of claims each made in the last 3 years, with the following results. f is the corresponding frequency. x 1 2 3 4 5 f 14 18 12 5 1 how many total claims are represented in the sample?
        a、15
        b、50
        c、111
        d、250

    2、an insurance company evaluates many numerical variables about a person before deciding on an appropriate rate for automobile insurance. a representative from a local insurance agency selected a random sample of insured drivers and recorded, x, the number of claims each made in the last 3 years, with the following results. f is the corresponding frequency. x 1 2 3 4 5 f 14 18 12 5 1 how many drivers are represented in the sample?
        a、5
        b、15
        c、18
        d、50

    3、a type of vertical bar chart in which the categories are plotted in the descending rank order of the magnitude of their frequencies is called a
        a、contingency table.
        b、pareto diagram.
        c、dot plot.
        d、pie chart.

    4、the width of each bar in a histogram corresponds to the
        a、differences between the bounaries of the class.
        b、number of observations in each class.
        c、midpont of each class.
        d、percentage of observations in each class.

    5、when polygons or histograms are constructed, which axis must show the true zero or "origin"?
        a、the horizontal axis.
        b、the vertical axis.
        c、both the horizontal axis and vertical axis.
        d、neither the horizontal nor the vertical axis.

    第三章 用数值度量描述数据(numerical descriptive measures)

    第三章测验题

    1、which ofthe following statistics is not a measure of central tendency?
        a、arithmetic mean.
        b、median.
        c、mode.
        d、q3.

    2、which of the arithmetic mean, median, mode, and geometric mean are resistant measures of central tendency?
        a、the arithmetric mean and median only.
        b、the median and mode only.
        c、the mode and geometric mean only.
        d、the arithmetic mean and mode only.

    3、in a right-skewed distribution
        a、the median equals the arithmetic mean.
        b、the median is less than the arithmetic mean.
        c、the median is larger than the arithmetic mean.
        d、none of the above.

    4、in a perfectly symmetrical bell-shaped "normal" distribution
        a、the arithmetic mean equals the median.
        b、the median equals the mode.
        c、the arithmetic mean equals the mode.
        d、all of the above.

    5、in general, which of the following descriptive summary measures cannot be easily approximated from a box-and-whisker plot?
        a、the variance.
        b、the range.
        c、the interquartile range.
        d、the median.

    第四章 抽样分布(sampling distributions)

    第四章测验题

    1、sampling distributions describe the distribution of
        a、parameters.
        b、statistics.
        c、both parameters and statistics.
        d、neither parameters nor statistics.

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

    3、the central limit theorem is important in statistics because
        a、for a large n, it says the population is approximately normal.
        b、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.
        d、for any sized sample, it says the sampling distribution of the sample mean is approximately normal.

    4、if the expectation of a sampling distribution is located at the parameter it is estimating, then we call that sampling distribution
        a、unbiased.
        b、minimum variance.
        c、biased.
        d、random.

    5、for air travelers, one of the biggest complaints is of the waiting time between when the airplane taxis away from the terminal until the flight takes off. this waiting time is known to have a skewed-right distribution with a mean of 10 minutes and a standard deviation of 8 minutes. suppose 100 flights have been randomly sampled. describe the sampling distribution of the mean waiting time between when the airplane taxis away from the terminal until the flight takes off for these 100 flights.
        a、distribution is skewed-right with mean=10 minutes and standard error=0.8 minutes.
        b、distribution is skewed-right with mean=10 minutes and standard error=8 minutes.
        c、distribution is approximately normal with mean=10 minutes and standard error=0.8 minutes.
        d、distribution is approximately normal with mean=10 minutes and standard error=8 minutes.

    第四章测验题

    1、sampling distributions describe the distribution of
        a、parameters.
        b、statistics.
        c、both parameters and statistics.
        d、neither parameters nor statistics.

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

    3、the central limit theorem is important in statistics because
        a、for a large n, it says the population is approximately normal.
        b、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.
        d、for any sized sample, it says the sampling distribution of the sample mean is approximately normal.

    4、if the expectation of a sampling distribution is located at the parameter it is estimating, then we call that sampling distribution
        a、unbiased.
        b、minimum variance.
        c、biased.
        d、random.

    5、for air travelers, one of the biggest complaints is of the waiting time between when the airplane taxis away from the terminal until the flight takes off. this waiting time is known to have a skewed-right distribution with a mean of 10 minutes and a standard deviation of 8 minutes. suppose 100 flights have been randomly sampled. describe the sampling distribution of the mean waiting time between when the airplane taxis away from the terminal until the flight takes off for these 100 flights.
        a、distribution is skewed-right with mean=10 minutes and standard error=0.8 minutes.
        b、distribution is skewed-right with mean=10 minutes and standard error=8 minutes.
        c、distribution is approximately normal with mean=10 minutes and standard error=0.8 minutes.
        d、distribution is approximately normal with mean=10 minutes and standard error=8 minutes.

    第五章 点估计(point estimation)

    第五章测验题

    1、if x has the binomial distribution with the number of total trials n=10 and the probability of success . in an experiment, we observed 4 successes, then an estimate of = .

    2、the diameter of a ball follows a normal distribution with mean m and standard deviation s. now we randomly draw 6 balls from a batch of product produced in a day and measure the diameter of each ball. we have the following observations (unit: mm): 14.70, 15.21, 14.90, 14.91, 15.32, 15.32. then, an unbiased estimate of m= .(correct to the second decimal place)

    3、the diameter of a ball follows a normal distribution with mean m and standard deviation s. now we randomly draw 6 balls from a batch of product produced in a day and measure the diameter of each ball. we have the following observations (unit: mm): 14.70, 15.21, 14.90, 14.91, 15.32, 15.32. then, an unbiased estimate of = .(correct to the third decimal place)

    4、the diameter of a ball follows a normal distribution with mean m and standard deviation s. now we randomly draw 6 balls from a batch of product produced in a day and measure the diameter of each ball. we have the following observations (unit: mm): 14.70, 15.21, 14.90, 14.91, 15.32, 15.32. then, a maximum likelihood estimate of = .(correct to the third decimal place)

    5、suppose that x has the following probability distribution: x 1 2 3 p q^2 2 q(1- q) (1- q)^2 where q (0< q<1) is an unknown parameter. now we obtain x1=1, x2=2, x3=1. then a moment estimate of q= .(correct to the second decimal place)

    6、suppose that x follows the following distribution: x 1 2 3 p q^2 2 q(1- q) (1- q)^2 where q (0< q<1) is an unknown parameter. now we obtain x1=1, x2=2, x3=1. then a maximum likelihood estimate of q= .(correct to the second decimal place)

    第六章 区间估计(confidence interval)

    第六章测验题

    1、the width of a confidence interval estimate for a proportion will be
        a、narrower for 99% confidence than for 95% confidence.
        b、wider for a sample size of 100 than for a sample size of 50.
        c、narrower for 90% confidence than for 95% confidence.
        d、narrower when the sample proportion is 0.50 than when the sample proportion is 0.20.

    2、the head librarian at the library of congress has asked her assistant for an interval estimate of the mean number of books checked out each day. the assistant provides the following interval estimate: from 740 to 920 books per day. if the head librarian knows that the population standard deviation is 150 books checked out per day, approximately how large a sample did her assistant use to determine the interval estimate?
        a、2
        b、3
        c、12
        d、it cannot be determined from the information given.

    3、if you were constructing a 99% confidence interval of the population mean based on a sample of n = 25, where the standard deviation of the sample s = 0.05, the critical value of t will be
        a、2.7969
        b、2.7874
        c、2.4922
        d、2.4851

    4、when determining the sample size for a proportion for a given level of confidence and sampling error, the closer to 0.50 that p is estimated to be, the __________ the sample size required.
        a、smaller
        b、larger
        c、sample size is not affected.
        d、the effect cannot be determined from the information given.

    5、private colleges and universities rely on money contributed by individuals and corporations for their operating expenses. much of this money is put into a fund called an endowment, and the college spends only the interest earned by the fund. a recent survey of 8 private colleges in the united states revealed the following endowments (in millions of dollars): 60.2, 47.0, 235.1, 490.0, 122.6, 177.5, 95.4, and 220.0. summary statistics yield =180.975 and s=143.042. calculate a 95% confidence interval for the mean endowment of all the private colleges in the united states, assuming a normal distribution for the endowments.
        a、$180.975$94.066
        b、$180.975$99.123
        c、$180.975$116.621
        d、$180.975$119.586

    第七章 假设检验基础:单个样本的假设检验(fundamentals of hypothesis testing: one-sample tests)

    第七章测验题

    1、which of the following would be an appropriate null hypothesis?
        a、the mean of a population is equal to 55.
        b、the mean of a sample is equal to 55.
        c、the mean of a population is greater than 55.
        d、only (a) and (c) are true.

    2、the power of a test is measured by its capability of
        a、rejecting a null hypothesis that is true.
        b、not rejecting a null hypothesis that is true.
        c、rejecting a null hypothesis that is false.
        d、not rejecting a null hypothesis that is false.

    3、if a test of hypothesis has a type i error probability () of 0.01, we mean
        a、if the null hypothesis is true, we don't reject it 1% of the time.
        b、if the null hypothesis is true, we reject it 1% of the time.
        c、if the null hypothesis is false, we don't reject it 1% of the time.
        d、if the null hypothesis is false, we reject it 1% of the time.

    4、how many kleenex should the kimberly clark corporation package of tissues contain? researchers determined that 60 tissues is the average number of tissues used during a cold. suppose a random sample of 100 kleenex users yielded the following data on the number of tissues used during a cold: = 52, s = 22. give the null and alternative hypotheses to determine if the number of tissues used during a cold is less than 60.
        a、h0: and h1: .
        b、h0: and h1: .
        c、h0: and h1: .
        d、h0: and h1: .

    5、how many kleenex should the kimberly clark corporation package of tissues contain? researchers determined that 60 tissues is the average number of tissues used during a cold. suppose a random sample of 100 kleenex users yielded the following data on the number of tissues used during a cold: = 52, s = 22. suppose the alternative we wanted to test was h1: . state the correct rejection region for
        a、reject h0 if t > 1.6604.
        b、reject h0 if t < – 1.6604.
        c、reject h0 if t > 1.9842 or z < – 1.9842.
        d、reject h0 if t < – 1.9842.

    第八章 两样本检验和单因素方差分析(two-sample tests and one-way anova)

    第八章测验题(1)

    1、the use of preservatives by food processors has become a controversial issue. suppose 2 preservatives are extensively tested and determined safe for use in meats. a processor wants to compare the preservatives for their effects on retarding spoilage. suppose 15 cuts of fresh meat are treated with preservative a and 15 are treated with preservative b, and the number of hours until spoilage begins is recorded for each of the 30 cuts of meat. the results are summarized in the table below. preservative a preservative b hours hours s a = 10.3 hours s b = 13.4 hours state the test statistic for determining if the population variances differ for preservatives a and b.
        a、f = – 3.10
        b、f = 0.5908
        c、f = 0.7687
        d、f = 0.8250

    2、if we are testing for the difference between the means of 2 related populations with samples of n1 = 20 and n2 = 20, the number of degrees of freedom is equal to
        a、39
        b、38
        c、19
        d、18

    3、in testing for differences between the means of two related populations, the null hypothesis is
        a、h0: .
        b、h0: .
        c、h0: .
        d、h0: .

    4、in testing for differences between the means of two independent populations, the null hypothesis is:
        a、h0:
        b、h0:
        c、h0:
        d、h0:

    5、given the following information, calculate , the pooled sample variance that should be used in the pooled-variance t test. n1 = 16, n2 = 25.
        a、
        b、
        c、
        d、

    第八章测验题(2)

    1、in a one-way anova, if the computed f statistic exceeds the critical f value, we may
        a、reject h0 since there is evidence all the means differ.
        b、reject h0 since there is evidence of a treatment effect.
        c、not reject h0 since there is no evidence of a difference.
        d、not reject h0 because a mistake has been made.

    2、which of the following components in an anova table are not additive?
        a、sum of squares
        b、degrees of freedom
        c、mean squares
        d、it is not possible to tell.

    3、why would you use the tukey-kramer procedure?
        a、to test for normality
        b、to test for homogeneity of variance
        c、to test independence of errors
        d、to test for differences in pairwise means

    4、in a one-way anova, the null hypothesis is always
        a、there is no treatment effect.
        b、there is some treatment effect.
        c、all the population means are different.
        d、some of the population means are different.

    5、as part of an evaluation program, a sporting goods retailer wanted to compare the downhill coasting speeds of 4 brands of bicycles. she took 3 of each brand and determined their maximum downhill speeds. the results are presented in miles per hour in the table below. trial barth tornado reiser shaw 1 43 37 41 43 2 46 38 45 45 3 43 39 42 46 suppose that the null hypothesis has been rejected at a 5% level of significance. the tukey-kramer procedure is now applied to make pairwise comparisons between groups. using an overall level of significance of 0.05, the critical value of the studentized range q used in calculating the critical range for the tukey-kramer procedure is (correct to the second decimal place) .

    第九章 简单线性回归(simple linear regression)

    第九章测验题

    1、a large national bank charges local companies for using their services. a bank official reported the results of a regression analysis designed to predict the bank’s charges (y) -- measured in dollars per month -- for services rendered to local companies. one independent variable used to predict service charge to a company is the company’s sales revenue (x) -- measured in millions of dollars. data for 21 companies who use the bank’s services were used to fit the model: the results of the simple linear regression are provided below.
        a、there is no practical interpretation, since a sales revenue of $0 is a nonsensical value.
        b、all companies will be charged at least $2,700 by the bank.
        c、about 95% of the observed service charges fall within $2,700 of the least squares line.
        d、for every $1 million increase in sales revenue, we expect a service charge to decrease $2,700.

    2、a large national bank charges local companies for using their services. a bank official reported the results of a regression analysis designed to predict the bank’s charges (y) -- measured in dollars per month -- for services rendered to local companies. one independent variable used to predict service charge to a company is the company’s sales revenue (x) -- measured in millions of dollars. data for 21 companies who use the bank’s services were used to fit the model: the results of the simple linear regression are provided below. interpret the p-value for testing whether exceeds 0.
        a、there is sufficient evidence (at the = 0.05) to conclude that sales revenue (x) is a useful linear predictor of service charge (y).
        b、there is insufficient evidence (at the = 0.10) to conclude that sales revenue (x) is a useful linear predictor of service charge (y).
        c、sales revenue (x) is a poor predictor of service charge (y).
        d、for every $1 million increase in sales revenue, we expect a service charge to increase $0.034.

    3、a large national bank charges local companies for using their services. a bank official reported the results of a regression analysis designed to predict the bank’s charges (y) -- measured in dollars per month -- for services rendered to local companies. one independent variable used to predict service charge to a company is the company’s sales revenue (x) -- measured in millions of dollars. data for 21 companies who use the bank’s services were used to fit the model: the results of the simple linear regression are provided below. a 95% confidence interval for is (15, 30). interpret the interval.
        a、we are 95% confident that the mean service charge will fall between $15 and $30 per month.
        b、we are 95% confident that the sales revenue (x) will increase between $15 and $30 million for every $1 increase in service charge (y).
        c、we are 95% confident that the average service charge (y) will increase between $15 and $30 for every $1 million increase in sales revenue (x).
        d、at the = 0.05 level, there is no evidence of a linear relationship between service charge (y) and sales revenue (x).

    4、a candy bar manufacturer is interested in trying to estimate how sales are influenced by the price of their product. to do this, the company randomly chooses 6 small cities and offers the candy bar at different prices. using candy bar sales as the dependent variable, the company will conduct a simple linear regression on the data below: city price ($) sales river falls 1.30 100 hudson 1.60 90 ellsworth 1.80 90 prescott 2.00 40 rock elm 2.40 38 stillwater 2.90 32 what is the estimated slope parameter for the candy bar price and sales data?
        a、161.386
        b、0.784
        c、– 3.810
        d、– 48.193

    5、a candy bar manufacturer is interested in trying to estimate how sales are influenced by the price of their product. to do this, the company randomly chooses 6 small cities and offers the candy bar at different prices. using candy bar sales as the dependent variable, the company will conduct a simple linear regression on the data below: city price ($) sales river falls 1.30 100 hudson 1.60 90 ellsworth 1.80 90 prescott 2.00 40 rock elm 2.40 38 stillwater 2.90 32 what is the coefficient of correlation for these data?
        a、– 0.8854
        b、– 0.7839
        c、0.7839
        d、0.8854

    期末考试卷

    final exam

    1、the process of using sample statistics to draw conclusions about true population parameters is called
        a、statistical inference
        b、the scientific method.
        c、sampling.
        d、descriptive statistics.

    2、the collection and summarization of the socioeconomic and physical characteristics of the employees of a particular firm is an example of
        a、descriptive statistics.
        b、inferential statistics.
        c、a parameter.
        d、a statistic.

    3、which of the following is most likely a population as opposed to a sample?
        a、registered voters in a county
        b、every third person to arrive at the bank
        c、the first 5 students completing an assignment
        d、respondents to a newspaper survey

    4、a summary measure that is computed to describe a characteristic from only a sample of the population is called
        a、a statistic.
        b、a parameter.
        c、a census.
        d、the scientific method.

    5、every spring semester, the school of business coordinates with local business leaders a luncheon for graduating seniors, their families, and friends. corporate sponsorship pays for the lunches of each of the seniors, but students have to purchase tickets to cover the cost of lunches served to the guests they bring with them. the following histogram represents the attendance at the senior luncheon, where x is the number of guests each graduating senior invited to the luncheon, and f is the number of graduating seniors in each category. how many graduating seniors attended the luncheon?
        a、275
        b、4
        c、152
        d、388

    6、a professor of economics at a small texas university wanted to determine which year in school students were taking his tough economics course. shown below is a pie chart of the results. what percentage of the class took the course prior to reaching their senior year?
        a、86%
        b、44%
        c、14%
        d、54%

    7、the following are the durations (in minutes) of a sample of long-distance phone calls made within the continental united states, reported by one long-distance carrier: time (in minutes) relative frequency 0 but less than 5 0.37 5 but less than 10 0.22 10 but less than 15 0.15 15 but less than 20 0.10 20 but less than 25 0.07 25 but less than 30 0.07 30 or more 0.02 if 100 calls were randomly sampled, how many calls lasted 15 minutes or longer?
        a、26
        b、10
        c、14
        d、74

    8、which of the following statistics is not a measure of central tendency?
        a、q3
        b、arithmetic mean
        c、median
        d、mode

    9、health care issues are receiving much attention in both academic and political arenas. a sociologist recently conducted a survey of citizens over 60 years of age whose net worth is too high to qualify for medicaid and have no private health insurance. the ages of 25 uninsured senior citizens were as follows: 60 61 62 63 64 65 66 68 68 69 70 73 73 74 75 76 76 81 81 82 86 87 89 90 92 identify which of the following is the correct statement.
        a、25% of the senior citizens sampled are older than 81 years of age.
        b、one fourth of the senior citizens sampled are below 64 years of age.
        c、the middle 50% of the senior citizens sampled are between 65.5 and 73.0 years of age.
        d、50% of the senior citizens sampled are below 65.5 years of age.

    10、in a perfectly symmetrical distribution,____.
        a、the range equals the interquartile range.
        b、the interquartile range equals the arithmetic mean.
        c、the median equals the arithmetic mean
        d、the variance equals the standard deviation.

    11、which descriptive summary measures are considered to be resistant statistics?____.
        a、the arithmetic mean and standard deviation
        b、the interquartile range and range
        c、the mode and variance
        d、the median and interquartile range

    12、according to the chebyshev rule, at least 93.75% of all observations in any data set are contained within a distance of how many standard deviations around the mean? ____.
        a、1
        b、2
        c、3
        d、4

    13、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 a standard deviation of 0.8 pounds. 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、0.0001
        b、0.0013
        c、0.0228
        d、0.4987

    14、the width of a confidence interval estimate for a proportion will be ____.
        a、narrower for 99% confidence than for 95% confidence
        b、wider for a sample size of 100 than for a sample size of 50
        c、narrower for 90% confidence than for 95% confidence
        d、narrower when the sample proportion is 0.50 than when the sample proportion is

    15、a confidence interval was used to estimate the proportion of statistics students that are female. a random sample of 72 statistics students generated the following 90% confidence interval: (0.438, 0.642). using the information above, what size sample would be necessary if we wanted to estimate the true proportion to within±0.08 using 95% confidence?____.
        a、105
        b、150
        c、420
        d、597

    16、which of the following would be an appropriate null hypothesis?
        a、the population proportion is no less than 0.65.
        b、the population proportion is less than 0.65.
        c、the sample proportion is less than 0.65.
        d、the sample proportion is no less than 0.65.

    17、a type ii error is committed when
        a、we don't reject a null hypothesis that is false.
        b、we reject a null hypothesis that is true.
        c、we don't reject a null hypothesis that is true.
        d、we reject a null hypothesis that is false.

    18、the owner of a local nightclub has recently surveyed a random sample of n = 250 customers of the club. she would now like to determine whether or not the mean age of her customers is over 30. if so, she plans to alter the entertainment to appeal to an older crowd. if not, no entertainment changes will be made. if she wants to be 99% confident in her decision, what rejection region should she use?
        a、reject h0 if t > 2.34.
        b、reject h0 if t < – 2.34.
        c、reject h0 if t < – 2.55.
        d、reject h0 if t > 2.58.

    19、a survey claims that 9 out of 10 doctors recommend aspirin for their patients with headaches. to test this claim against the alternative that the actual proportion of doctors who recommend aspirin is less than 0.90, a random sample of 100 doctors was selected. suppose you reject the null hypothesis. what conclusion can you draw?
        a、there is sufficient evidence that the proportion of doctors who recommend aspirin is less than 0.90.
        b、there is not sufficient evidence that the proportion of doctors who recommend aspirin is not less than 0.90.
        c、there is sufficient evidence that the proportion of doctors who recommend aspirin is not less than 0.90.
        d、there is not sufficient evidence that the proportion of doctors who recommend aspirin is less than 0.90.

    20、a major videocassette rental chain is considering opening a new store in an area that currently does not have any such stores. the chain will open if there is evidence that more than 5,000 of the 20,000 households in the area are equipped with videocassette recorders (vcrs). it conducts a telephone poll of 300 randomly selected households in the area and finds that 96 have vcrs. the p-value associated with the test statistic in this problem is approximately equal to:
        a、0.0026.
        b、0.0100.
        c、0.0051.
        d、0.0013.

    21、the use of preservatives by food processors has become a controversial issue. suppose 2 preservatives are extensively tested and determined safe for use in meats. a processor wants to compare the preservatives for their effects on retarding spoilage. suppose 15 cuts of fresh meat are treated with preservative a and 15 are treated with preservative b, and the number of hours until spoilage begins is recorded for each of the 30 cuts of meat. the results are summarized in the table below. preservative a preservative b a = 106.4 hours b = 96.54 hours sa = 10.3 hours sb = 13.4 hours state the test statistic for determining if the population variances differ for preservatives a and b.
        a、f = 0.5908
        b、f = – 3.10
        c、f = 0.7687
        d、f = 0.8250

    22、when testing h0:μ1−μ2≤0 versush1:μ1−μ2>0 , the observed value of the z-score was found to be – 2.13. the p-value for this test would be
        a、0.9834.
        b、0.0166.
        c、0.0332.
        d、0.9668.

    23、to test the effects of a business school preparation course, 8 students took a general business test before and after the course. the results are given below. exam score exam score student before course (1) after course (2) 1 530 670 2 690 770 3 910 1,000 4 700 710 5 450 550 6 820 870 7 820 770 8 630 610 at the 0.05 level of significance, the decision for this hypothesis test would be:
        a、reject the null hypothesis.
        b、do not reject the null hypothesis.
        c、reject the alternative hypothesis.
        d、it cannot be determined from the information given.

    24、in a one-way anova, if the computed f statistic exceeds the critical f value, we may
        a、reject h0 since there is evidence of a treatment effect.
        b、reject h0 since there is evidence all the means differ.
        c、not reject h0 since there is no evidence of a difference.
        d、not reject h0 because a mistake has been made.

    25、an airline wants to select a computer software package for its reservation system. four software packages (1, 2, 3, and 4) are commercially available. the airline will choose the package that bumps as few passengers, on average, as possible during a month. an experiment is set up in which each package is used to make reservations for 5 randomly selected weeks. (a total of 20 weeks was included in the experiment.) the number of passengers bumped each week is obtained, which gives rise to the following excel output: anova source of variation ss df ms f p-value f crit between groups 212.4 8.304985 0.001474 3.238867 within groups 136.4 8.525 total 348.8 the among group mean squares is
        a、70.8.
        b、8.525.
        c、212.4
        d、637.2.

    26、an airline wants to select a computer software package for its reservation system. four software packages (1, 2, 3, and 4) are commercially available. the airline will choose the package that bumps as few passengers, on average, as possible during a month. an experiment is set up in which each package is used to make reservations for 5 randomly selected weeks. (a total of 20 weeks was included in the experiment.) the number of passengers bumped each week is obtained, which gives rise to the following excel output: anova source of variation ss df ms f p-value f crit between groups 212.4 8.304985 0.001474 3.238867 within groups 136.4 8.525 total 348.8 at a significance level of 1%,
        a、there is sufficient evidence to conclude that the average numbers of customers bumped by the 4 packages are not all the same.
        b、there is insufficient evidence to conclude that the average numbers of customers bumped by the 4 packages are not all the same.
        c、there is insufficient evidence to conclude that the average numbers of customers bumped by the 4 packages are not all the same.
        d、there is sufficient evidence to conclude that the average numbers of customers bumped by the 4 packages are all the same.

    27、the slope (b1) represents
        a、the estimated average change in y per unit change in x.
        b、predicted value of y when x = 0.
        c、the predicted value of y.
        d、variation around the line of regression.

    28、for air travelers, one of the biggest complaints involves the waiting time between when the airplane taxis away from the terminal until the flight takes off. this waiting time is known to have a skewed-right distribution with a mean of 10 minutes and a standard deviation of 8 minutes. suppose 100 flights have been randomly sampled. describe the sampling distribution of the mean waiting time between when the airplane taxis away from the terminal until the flight takes off for these 100 flights.
        a、distribution is approximately normal with mean = 10 minutes and standard error = 0.8 minutes.
        b、distribution is skewed-right with mean = 10 minutes and standard error = 0.8 minutes.
        c、distribution is skewed-right with mean = 10 minutes and standard error = 8 minutes.
        d、distribution is approximately normal with mean = 10 minutes and standard error = 8 minutes

    29、a major department store chain is interested in estimating the average amount its credit card customers spent on their first visit to the chain’s new store in the mall. fifteen credit card accounts were randomly sampled and analyzed with the sample mean 50.5 dollars and sample variance 400. construct a 95% confidence interval for the average amount its credit card customers spent on their first visit to the chain’s new store in the mall, assuming that the amount spent follows a normal distribution.
        a、$50.50 ± $11.08
        b、$50.50 ± $9.09
        c、$50.50 ± $10.12
        d、$50.50 ± $11.00

    30、suppose a sample of n = 50 items is drawn from a population of manufactured products and the weight, x, of each item is recorded. prior experience has shown that the weight has a probability distribution with mean 6 ounces and standard deviation 2.5 ounces. which of the following is true about the sampling distribution of the sample mean if a sample of size 15 is selected?
        a、the mean of the sampling distribution is 6 ounces.
        b、the standard deviation of the sampling distribution is 2.5 ounces.
        c、the shape of the sample distribution is approximately normal.
        d、none.

    31、suppose that x1 and x2 are random sample independently drawn from a population x with mean m and standard deviation s. which one of the following statistics is the best estimator of m?
        a、12x1 12x2
        b、14x1 34x2
        c、13x1 23x2
        d、15x1 45x2

    32、it is desired to estimate the average total compensation of ceos in the service industry. data were randomly collected from 18 ceos and the 97% confidence interval was calculated to be (2,181,260,5,836,180). which of the following interpretations is correct?
        a、97% of the sampled total compensation values fell between 2,181,260and5,836,180
        b、we are 97% confident that the average total compensation of all ceos in the service industry falls in the interval 2,181,260to5,836,180
        c、we are 97% confident that the mean of the sampled ceos falls in the interval 2,181,260to5,836,180
        d、in the population of service industry ceos, 97% of them will have total compensations that fall in the interval 2,181,260to5,836,180

    33、suppose that the height of adult female x (unit: meters) follows a normal distribution with meanμand varianceσ2. we drew a random sample from this population and observed: 1.65, 1.54, 1.70, 1.63, 1.58, 1.72, 1.56, 1.60. then the maximum likelihood estimate of σ2 is[填空1](correct to the fourth decimal place)

    34、suppose that the height of adult female x (unit: meters) follows a normal distribution with mean μand varianceσ2. we drew a random sample from this population and observed: 1.65, 1.54, 1.70, 1.63, 1.58, 1.62, 1.56, 1.60. then the moment estimate of μ is [填空1](correct to the second decimal place)

    35、the managers of a brokerage firm are interested in finding out if the number of new clients a broker brings into the firm affects the sales generated by the broker. they sample 12 brokers and determine the number of new clients they have enrolled in the last year and their sales amounts in thousands of dollars. these data are presented in the table that follows. broker clients sales 1 27 52 2 11 37 3 42 64 4 33 55 5 15 29 6 15 34 7 25 58 8 36 59 9 28 44 10 30 48 11 17 31 12 22 38 the least squares estimate of the slope is [填空1].(correct to the second decimal place)

    36、the managers of a brokerage firm are interested in finding out if the number of new clients a broker brings into the firm affects the sales generated by the broker. they sample 12 brokers and determine the number of new clients they have enrolled in the last year and their sales amounts in thousands of dollars. these data are presented in the table that follows. broker clients sales 1 27 52 2 11 37 3 42 64 4 33 55 5 15 29 6 15 34 7 25 58 8 36 59 9 28 44 10 30 48 11 17 31 12 22 38 the least squares estimate of the y intercept is [填空1].(correct to the first decimal place)

    37、the managers of a brokerage firm are interested in finding out if the number of new clients a broker brings into the firm affects the sales generated by the broker. they sample 12 brokers and determine the number of new clients they have enrolled in the last year and their sales amounts in thousands of dollars. these data are presented in the table that follows. broker clients sales 1 27 52 2 11 37 3 42 64 4 33 55 5 15 29 6 15 34 7 25 58 8 36 59 9 28 44 10 30 48 11 17 31 12 22 38 the prediction for the amount of sales (in $1,000s) for a person who brings 25 new clients into the firm is[填空1].(correct to the second decimal place)

    38、the managers of a brokerage firm are interested in finding out if the number of new clients a broker brings into the firm affects the sales generated by the broker. they sample 12 brokers and determine the number of new clients they have enrolled in the last year and their sales amounts in thousands of dollars. these data are presented in the table that follows. broker clients sales 1 27 52 2 11 37 3 42 64 4 33 55 5 15 29 6 15 34 7 25 58 8 36 59 9 28 44 10 30 48 11 17 31 12 22 38 [填空1]% of the total variation in sales generated can be explained by the number of new clients brought in.(correct to the first decimal place)

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