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# QNT 351 FINAL EXAM AUGUST 2017

## 1. The mean amount spent by a family of four on food is \$500 per month with a standard deviation of \$75. Assuming that the food costs are normally distributed, what is the probability that a family spends less than \$410 per month? 0.1151 0.0362 0.8750 0.2158 2. As the size of the sample increases, what happens to the shape of the distribution of sample means? It cannot be predicted in advance. It is negatively skewed. It approaches a normal distribution. It is positively skewed. 3. What is the following table called? Ages Number of Ages 20 up to 30 16 30 up to 40 25 40 up to 50 51 50 up to 60 80 60 up to 70 20 70 up to 80 8 Frequency polygon Frequency distribution Histogram Cumulative frequency distribution 4. How is the t distribution similar to the standard z distribution? Both are continuous distributions. Both are skewed distributions. Both are families of distributions. Both are discrete distributions. 5. In a distribution, the second quartile corresponds with the __________. Median Variance Mean Mode 6. A random sample of 85 supervisors revealed that they worked an average of 6.5 years before being promoted. The population standard deviation was 1.7 years. Using the 0.95 degree of confidence, what is the confidence interval for the population mean? 6.99 and 7.99 6.14 and 6.86 4.15 and 7.15 6.49 and 7.49 x±z(S/n) x±z(s/√(n)) 7. Incomes of 50 loan applicants are obtained. Which level of measurement is income? Ordinal Nominal Ratio Interval 8. Which of the following is an example of a continuous variable? Zip codes of shoppers. Number of students in a statistics class. Tons of concrete to complete a parking garage. Rankings of baseball teams in a league. 9. For the normal distribution, the mean plus and minus two standard deviations will include about what percent of the observations? 99.7% 68% 50% 95% 10. The main purpose of descriptive statistics is to: Summarize data in a useful and informative manner. Determine if the data adequately represents the population. Make inferences about a population. Gather or collect data. 11. Which of the following is true regarding the normal distribution? The points of the curve meet the x-axis at z = -3 and z = 3. It is asymmetrical. It has two modes. The mean, median, and mode are all equal. 12. What is the relationship among the mean, median, and mode in a symmetric distribution? The mean is always the smallest value. They are all equal. The mean is always the largest value. The mode is the largest value. 13. The probability distribution for the number of automobiles lined up at a Lakeside Olds dealer at opening time (7:30 a.m.) for service is: Number Probability 1 0.05 2 0.30 3 0.40 4 .25 On a typical day how many automobiles should Lakeside Olds expect to be lined up at opening time? Use expected value or mean of the probability distribution. 2.85 1.00 10.00 1.96 14. Which of the following is a point estimate for the population mean (µ)? X” x/n s σ 15. When all the items in a population have an equal chance of being selected for a sample the process is called _________________. Simple random sampling Z-score Non-probability sampling Sampling error 16. A student was interested in the cigarette smoking habits of college students and collected data from an unbiased random sample of students. The data is summarized in the following table: Males who smoke 20 Males who do not smoke 30 Females who smoke 25 Females who do not smoke 50 What type of chart best represents relative class frequencies? Pie chart Scatter plot Frequency polygon Box plot 17. A listing of all possible outcomes of an experiment and their corresponding probabilities of occurrence is called a ____________. Probability distribution Random variable Frequency distribution Subjective probability 18. The distribution of a sample of the outside diameters of PVC pipes approximates a symmetrical bell-shaped distribution. The arithmetic mean is 14.0 inches, and the standard deviation is 0.1 inches. About 68% of the outside diameters lie between what two amounts? 13.8 and 14.2 inches 13.5 and 14.5 inches 13.9 and 14.1 inches 13.0 and 15.0 inches 19. For the past week a company’s common stock closed with the following prices: \$61.5, \$62, \$61.25, \$60.875, and \$61.5. What was the price range? \$1.750 \$1.875 \$1.250 \$1.125 20. Judging from recent experience 5% of the computer keyboards produced by an automatic high-speed machine are defective. If six keyboards are randomly selected, what is the probability that none of the keyboards are defective? Use binomial distribution. 0.500 0.001 0.735 0.167 21. The National Center for Health Statistics reported that of every 883 deaths in recent years, 24 resulted from an automobile accident, 182 from cancer, and 333 from heart disease. What is the probability that a particular death is due to an automobile accident? 539/883 or 0.610 182/883 or 0.206 24/333 or 0.072 24/883 or 0.027 22. The mean of a normal probability distribution is 500 and the standard deviation is 10. About 95% of the observations lie between what two values? 350 and 650 475 and 525 400 and 600 480 and 520 23. Which of the following is a characteristic of the normal probability distribution? It’s bell-shaped. It’s asymmetrical. It’s rectangular. It’s positively skewed. 24. Refer to the following breakdown of responses to a survey of “Are you concerned about being tracked while connected to the Internet?” Response Frequency Very concerned 140 Somewhat concerned 40 No concern 20 What is the class with the greatest frequency? Very concerned No concern None apply Somewhat concerned 25. The names of the positions in a corporation such as chief operating officer or controller are examples of what type of variable? Interval Ratio Quantitative Qualitative 26. The members of each basketball team wear numbers on their jerseys. What scale of measurement are these numbers considered? Interval Nominal Ratio Ordinal 27. A portion or part of a population is called a: Random survey Frequency distribution Sample Tally 28. Mileage tests were conducted on a randomly selected sample of 100 newly developed automobile tires. The results showed that the mean tread life was 50,000 miles, with a standard deviation of 3,500 miles. What is the best estimate of the mean tread life in miles for the entire population of these tires? 3,500 500 35 50,000 29. A large manufacturing firm tests job applicants. Test scores are normally distributed with a mean of 500 and a standard deviation of 50. Management is considering placing a new hire in an upper-level management position if the person scores in the upper sixth percent of the distribution. What is the lowest score a new hire must earn to qualify for a responsible position? 625 50 460 578 30. The following graph is a: Box plot Contingency table Dot plot Stem-and-leaf display

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