Maryland STATSTAT 230Stat 230 Midterm
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STAT 230 100 POINTS
Midterm Exam (120 POINTS POSSIBLE)
Spring 2013
OPEN BOOK/OPEN NOTES/Calculators Needed
(Maximum Time-3 Hours)
Circle the best answer for each question
Use the following data for questions 1 through 4: 5,12,6,8,5,6,7,5,12,4.
1. The median is
a. 5
b. 6
c. 7
d. 8
e. None of the above
2. The mode is
a. 5
b. 6
c. 7
d. 8
e. None of the above
3. The mean is
a. 5
b. 6
c. 7
d. 8
e. None of the above
4. The 75th percentile is
a. 5
b. 6
c. 7
d. 8
e. None of the above
Use the following data for questions 5 through 9: 3,5,12,3,2.
5. The variance is
a. 80
b. 4.062
c. 13.2
d. 16.5
e. None of the above
6. The standard deviation is
a. 8.994
b. 4.062
c. 13.2
d. 16.5
e. None of the above
7. The coefficient of variation is
a. 72.66%
b. 81.24%
c. 264%
d. 330%
e. None of the above
8. The range is
a. 1
b. 2
c. 10
d. 12
e. None of the above
9. The interquartile range is
a. 1
b. 2
c. 10
d. 12
e. None of the above
10. If A and B are independent events with P(A) = 0.4 and P(B) = 0.6, then
P(A l B) =
a. 0.76
b. 1.00
c. 0.24
d. 0.2
e. None of the above = 0.4
11. If A and B are independent events with P(A) = 0.2 and P(B) = 0.6, then
P(A U B) =
a. 0.62
b. 0.12
c. 0.60
d. 0.68
e. None of the above
12. If A and B are independent events with P(A) = 0.05 and P(B) = 0.65,
then P(A l B) =
a. 0.05
b. 0.0325
c. 0.65
d. 0.8
e. None of the above
13. If A and B are mutually exclusive events with P(A) = 0.3 and P(B) =
0.5, then P(A U B) =
a. 0.30
b. 0.15
c. 0.00
d. 0.8
e. None of the above
14. If A and B are independent with P(A) = 0.3 and P(B) =
0.5, then P(A intersect B) =
a. 0.00
b. 0.15
c. 0.8
d. 0.2
e. None of the above
15. A lottery is conducted using three urns. Each urn contains chips
numbered from 0 to 9. One chip is selected at random from each
urn. The total number of sample points in the sample space is
a. 30
b. 100
c. 729
d. 1000
e. None of the above
16. A six-sided die is tossed three times. The probability of observing
three ones in a row is
a. 1/3
b. 1/6
c. 1/27
d. 1/216
e. None of the above
17. A perfectly balanced coin is tossed 6 times and tails appears on all six
tosses. Then, on the seventh toss
a. tails cannot appear
b. heads has a much larger chance of appearing than tails
c. tails has a better chance of appearing than heads
d. heads must appear
e. None of the above
18. In a questionnaire, respondents are asked to mark their gender as male or female. Gender is an example of the
a. ordinal scale
b. nominal scale
c. ratio scale
d. interval scale
19. A random variable that can assume only a finite number of values is
referred to as a(n)
a. infinite sequence
b. finite sequence
c. discrete random variable
d. discrete probability function
e. None of the above
20. A continuous random variable may assume
a. any value in the interval or collection of intervals
b. only integral values in an interval or collection of intervals
c. only fractional values in an interval or collection of intervals
d. only the positive integral values in an interval
e. None of the above
21. What is the probability that among the students in the sample exactly
two are female if 8 students are randomly selected from a large student
body that is 60% female?
a. 0.0896
b. 0.2936
c. 0.0413
d. 0.0007
e. None of the above
22. The number of electrical outages in a city varies from day to day.
Assume the following probability for x (number of outages)
x f(x)
0 0.80
1 0.15
2 0.04
3 0.01
The mean and standard deviation for the number of outages are
a. 2.6 and 5.77
b. 0.26 and 0.577
c. 3 and 0.01
d. 0 and 0.8
e. 1.25 and 1.25
23. The weight of an object is an example of
a. a continuous random variable
b. a discrete random variable
c. either a continuous or a discrete random variable, depending on the
weight of the object
d. either a continuous or a discrete random variable, depending on the
units of measure
e. None of the above
24. Four percent of the customers of a mortgage company default on their
payments. A sample of five customers is selected. What is the
probability that exactly two customers in the sample will default on
their payments?
a. 0.2592
b. 0.0142
c. 0.9588
d. 0.7408
e. 0.0000
25. A local bottling company has determined the number of machine
breakdowns per month and their respective probabilities as shown
below:
Number of Breakdowns Probability
0 0.15
1 0.35
2 0.25
3 0.20
4 0.05
The expected number of breakdowns per month is
a. 2
b. 1.65
c. one since it has the highest probability
d. at least 4
e. None of the above
26. The Poisson probability distribution is a
a. continuous probability distribution
b. discrete probability distribution
c. uniform probability distribution
d. normal probability distribution
e. None of the above
Using the following probability distribution for questions 27 and 28
x f(x)
10 .2
20 .3
30 .4
40 .1
27. The expected value of x equals
a. 24
b. 25
c. 30
d. 100
e. None of the above
28. The variance of x equals
a. 9.165
b. 84
c. 85
d. 93.33
e. None of the above
For questions 29 through 33 consider the following: The random variable x, which is the number of occurrences of an event over an interval of ten minutes. It can be assumed that the probability of an occurrence is the same in any two time periods of an equal length. It is known that the mean number of occurrences in ten minutes is 5.3.
29. The random variable is
a. Bernoulli
b. Poisson
c. Binomial
d. Unknown
e. None of the above
30. The random variable x is
a. discrete
b. continuous
c. either a or b depending on how the interval is defined
d. not enough information is given
e. None of the above
31. The expected value of the random variable x is
a. 2
b. 5.3
c. 10
d. 2.30
e. None of the above
32. The probability that there are 8 occurrences in ten minutes is
a. .0241
b. .0771
c. .1126
d. .9107
e. None of the above
33. The probability that there are less than 3 occurrences is
a. .0659
b. .0948
c. .1016
d. .1239
e. None of the above
34. Z is a standard normal random variable. The P(-1.20< =Z<=1.50) =
a. 0.0483
b. 0.3849
c. 0.4332
d. 0.8181
e. None of the above
35. The probability of a player weighing more than 241.25 pounds on a team with the mean weight of 200 pounds and a standard deviation of 25
pounds is
a. 0.4505
b. 0.0495
c. 0.9505
d. 0.9010
e. None of the above
36. Five hundred residents of a city are polled to obtain information on voting intentions in an upcoming city election. The five hundred residents in this study is an example of a(n)
a. Census
b. Sample
c. observation
d. population
37. The process of analyzing sample data in order to draw conclusions about the characteristics of a population is called
a. descriptive statistics
b. statistical inference
c. data analysis
d. data summarization
38. The sum of the percent frequencies for all classes will always equal
a. One
b. the number of classes
c. the number of items in the study
d. 100
Exhibit 2-2
A survey of 800 college seniors resulted in the following crosstabulation regarding their undergraduate major and whether or not they plan to go to graduate school.
Undergraduate Major
Graduate School Business Engineering Others Total
Yes 70 84 126 280
No 182 208 130 520
Total 252 292 256 800
39. Refer to Exhibit 2-2 above. Of those students who are majoring in business, what percentage plans to go to graduate school?
a. 27.78
b. 8.75
c. 70
d. 72.22
The manager of Corner Convenience Store would like to know how quickly customers are able to make their purchases. The manager observed customers and recorded the amount of time (in seconds) it took for each customer to check out. She then constructed the following chart:
40. Refer to Exhibit 3-3 above.
What type of chart is this?
a. Pareto
b. Ogive
c. Histogram
d. BarChart
9 years ago
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