《统计学》样卷

Find the mean.( )A.2B.1.9C.6D.0.25 7.Forty percent of marriages end in divorce.You randomly select 15 married couples. Find the probability exactly 5 of the marriages will end in divorce.( )A.0.160B.0.015C.0.46D.0.033 8.A random sample of 15 DVD players has a mean price of $64.30 and a standard deviation of $5.60. Find a 95% confidence interval for the mean price of all DVD players. ( )A.(61.20,67.40)B.(61.47,67.13)C.(61.22,67.38)D.(61.10,67.51)9.Determin the minimum sample size needed to construct a 95% confidence interval for the mean age of employees at a company.The estimate must be accurate to within 0.5 year.Assume the standard deviation is 4.8 years.( )A.18B.19C.354D.355 10.State the null and alternative hypotheses.A student claims the mean cost of a textbook is at least $125.( ) A.0:125,:125a H H μμ>≤ B.0:125,:125a H H μμ<≥ C.0:125,:125a H H μμ≤> D.0:125,:125a H H μμ≥<11.You are testing the claim that the mean cost of a new car is more than $25,200.How should you interpret a decision that rejects the null hypothesis?( ) A.There is enough evidence to reject the claim B.There is enough evidence to support the claim C.There is not enough evidence to reject the claim D.There is not enough evidence to support the claim e technology to find the P-value for the following test: H 0: μ ≤ 20 H a : μ > 20 ,21.3x =,s = 2.1,n = 16 ( )A.0.0128B.0.0257C.0.9872D.0.0066 13.Calculate the correlation coefficient r,for temperature (x) and number of cups of coffee sold per hour (y).( )A.0.946B.-0.973C.-2.469D.81.76014.Determine the type of correlation between the variables. ( )A.Positive linear correlationB.Negative linear correlationC.No linear correlationD.Not sure15.The equation of the regression line for temperature (x) and number of cups of coffee sold per hour (y) is0.38332.139=-+.Predict the number of cups of coffee sold pery xhour when the temperature is 48°( )A.41.4B.30.7C.13.8D.50.5二、The life span of a car battery is normally distributed,with a mean of 44 months and a standard deviation of 5 months.(a)A car battery is selected at random.Find the probability that the life span of the battery is less than 36 months.(b)A car battery is selected at random.Find the probability that the life span of the battery is between 42 and 60 months.(c)What is the shortest life expectancy a car battery can have and still be in the top 5% of life expectancies?(1.6)0.9452,(3.2)0.9993,(0.4)0.6554,(1.645)0.95====F F F F三、Weekly salaries (in dollars) for a sample of registered nurses are listed.774 446 1019 795 908 667 444 960(a)Find the mean,the median,and the mode of the salaries.Which best describes a typical salary?(b)Find the range,variance,and standard deviation of the data set.Interpret the results in the context of the real-life setting.四、A survey of employees in the United States found that 56% do not use all of theirvacation time.Y ou randomly select 30 employees and ask them if they use all of their vacation time.(a)V erify that the normal distribution can be used to approximate the binomial distribution.(b)Find the probability that at most 14 employees say they do not use all of their vacation time.五、The data set is the number of minutes a sample of 25 people exercise each week.108 139 120 123 120 132 123 131 131 118 114 127 119157 150 124 111 101 135 119 116 117 127 128 139(a)Make a frequency distribution of the data set using five classes.Include class limits,midpoints,frequencies,relative frequencies and cumulative frequencies.(b)Display the data using a frequency histogram.(c)Describle the distribution’s shape as symmetric,uniform,or skewed.(d)Display the data using a box-and-whisker plot.六、A citrus grower’s association believes that the mean utilization of fresh citrus fruits by people in the United States is at least 22 pounds per year.A random sample of 103 people in the United States has a mean utilization of fresh citrus fruits of 21.6 pounds per year and a standard deviation of 7 pounds.At a=0.05,can you reject the association’s claim that the mean utilization of fresh citrus fruits by people in the United States is at least 22 pounds per year?七、The number of hours 13 students spent studying for a test and their scores on that(a)Display the data in a scatter plot;(b)Calculate the correlation coefficient r;(c)Make a conclusion about the type of correlation。