# QNT 351 Week 5 Final Exam

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QNT/351

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QNT 351 Week 5 Final Exam

1.      How is the t distribution similar to the standard z distribution?

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Both are families of distributions.

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Both are skewed distributions.

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Both are discrete distributions.

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Both are continuous distributions.

2.       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?

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350 and 650

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475 and 525

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480 and 520

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400 and 600

3.      As the size of the sample increases, what happens to the shape of the distribution of sample means?

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It is positively skewed.

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It cannot be predicted in advance.

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It approaches a normal distribution.

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It is negatively skewed.

4.      The names of the positions in a corporation, such as chief operating officer or controller, are examples of what type of variable?

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Interval

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Qualitative

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Quantitative

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Ratio

5.      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?

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500

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3,500

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35

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50,000

6.      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?

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182/883 or 0.206

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539/883 or 0.610

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24/333 or 0.072

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24/883 or 0.027

7.      Which of the following is true regarding the normal distribution?

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The points of the curve meet the x-axis at z = -3 and z = 3.

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The mean, median, and mode are all equal.

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It is asymmetrical.

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It has two modes.

8.      The following graph is a:

Stem-and-leaf display

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Dot plot

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Contingency table

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Box plot

9.      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.

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0.167

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0.500

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0.735

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0.001

10.  The members of each basketball team wear numbers on their jerseys. What scale of measurement are these numbers considered?

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Ratio

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Interval

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Ordinal

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Nominal

11.   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

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Frequency distribution

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Histogram

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Cumulative frequency distribution

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Frequency polygon

12.  Which of the following is a characteristic of the normal probability distribution?

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It’s bell-shaped.

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It’s rectangular.

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It's positively skewed.

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It’s asymmetrical.

13.  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?

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13.0 and 15.0 inches

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13.9 and 14.1 inches

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13.8 and 14.2 inches

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13.5 and 14.5 inches

14.  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?

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0.1151

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0.8750

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0.0362

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0.2158

15.  For the normal distribution, the mean plus and minus two standard deviations will include about what percent of the observations?

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68%

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99.7%

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50%

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95%

16.  Which of the following is an example of a continuous variable?

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Rankings of baseball teams in a league.

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Number of students in a statistics class.

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Tons of concrete to complete a parking garage.

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Zip codes of shoppers.

17.  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?

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None apply

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No concern

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Somewhat concerned

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Very concerned

18.  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?

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Box plot

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Pie chart

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Frequency polygon

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Scatter plot

19.  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.

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2.85

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1.00

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1.96

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10.00

20.  A portion or part of a population is called a:

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Frequency distribution

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Random survey

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Tally

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Sample

21.  What is the relationship among the mean, median, and mode in a symmetric distribution?

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The mode is the largest value.

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The mean is always the largest value.

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They are all equal.

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The mean is always the smallest value.

22.  In a distribution, the second quartile corresponds with the __________.

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Mean

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Mode

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Variance

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Median

23.  Which of the following is a point estimate for the population mean (µ)?

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s

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x bar

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x/n

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σ

24.  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?

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4.15 and 7.15

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6.49 and 7.49

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6.99 and 7.99

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6.14 and 6.86

25.  A listing of all possible outcomes of an experiment and their corresponding probabilities of occurrence is called a ____________.

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Random variable

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Frequency distribution

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Subjective probability

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Probability distribution

26.  Incomes of 50 loan applicants are obtained. Which level of measurement is income?

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Nominal

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Ordinal

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Ratio

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Interval

27.  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?

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\$1.250

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\$1.125

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\$1.750

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\$1.875

28.  When all the items in a population have an equal chance of being selected for a sample, the process is called _________________.

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Sampling error

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Simple random sampling

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Non-probability sampling

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Z-score

29.  The main purpose of descriptive statistics is to:

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Determine if the data adequately represents the population.

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Summarize data in a useful and informative manner.

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Gather or collect data.

30.  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?

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578

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50

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625

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460