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Stat 200: Quiz 2 
Multiple-choice: Choose only one answer in each question.
Submit only the answers!
There are 27 problems, 80 points total.
01. The Complement rule states that the probability of an event not occurring is
A equal to one minus the probability it will occur.
B equal to one minus the probability it will not occur.
C equal to 0.0
D equal to 1.0
E none of the above
Consider the following to answer the next three questions:
The option to buy extended warranties is commonplace with most electronics purchases. Data for
420 consumers who purchased digital cameras and laptop computers from a leading electronics
retailer are summarized in the table.
Purchase Warranty?
Yes No Total
Digital Camera 30 42 72
Laptop Computer 145 203 348
Total 175 245 420
02. The probability that a consumer does not purchase an extended warranty is
A 0.07
B 0.42
C 0.58
D 0.17
E None of the above
03. The probability that a consumer purchases a digital camera and an extended warranty is
A 0.07
B 0.42
C 0.58
D 0.17
E None of the above
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04. The probability that a consumer purchases an extended warranty given that he/she has
purchased a digital camera is
A 0.07
B 0.42
C 0.58
D 0.17
E None of the above
05. A recent survey of local cell phone retailers showed that of all cell phones sold last month,
64% had a camera, 28% had a music player and 22% had both. The probability that a cell phone
sold last month had a camera or a music player is
A 0.22
B 0.70
C 0.92
D 0.30
E None of the above
06. In how many different ways can a work party of 4 be chosen from 9 volunteers?
A 4
B 36
C 126
D 3024
E None of the above
07. Find the standard deviation of the distribution:
X P(X)
0 0.45
1 0.44
2 0.09
3 0.02
A 0.52
B 0.72
C 0.99
D 0.98
E none of these
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08. Suppose that in a certain town, 90% of the voters favor a new ball park. Find the probability
that among 6 voters questioned, 5 of them favor the new ball park.
A 0.590
B 0.354
C 0.833
D 0.531
E none of the above
09. A gambler pays $5 to play a game of dice. If he rolls a sum of 10 the house pays him $10; if
he rolls a sum of 3 the house pays him $20, otherwise he loses. What is the expectation of this
game?
A -$2.36
B $2.36
C -$2.78
D -$3.06
E none of the above
10. Consider the Standard Normal distribution. Find the probability that z < 1.13.
A 0.8485
B 0.1292
C 0.8907
D 0.8708
E None of the above
11. Consider the Standard Normal distribution. Find the probability that z < -1.81.
A 0.0359
B 0.0351
C -0.0351
D 0.9649
E None of the above
12. Consider the Standard Normal distribution. Find P(z > 0.59)
A 0.7224
B 0.2190
C 0.2224
D 0.2776
E None of the above
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13. Consider the Standard Normal distribution. Find the probability P(-1.10 < z < -0.36).
A 0.4951
B 0.2237
C 0.2239
D -0.2237
E None of the above
14. Consider the Standard Normal curve. Find the value of z such that the area to the right of z
is 67% of the total area.
A 0.44
B -0.44
C 1.00
D -1.50
E None of the above
15. Consider the Standard Normal curve. Find the value of z such that the area to the right of z
is 2% of the total area.
A 2.05
B 2.06
C -2.05
D 2.10
E None of the above
16. Find the critical value z* for the 97% confidence interval.
A 1.88
B 2.07
C 1.96
D 2.17
E. None of the above
17. The mean amount spent by a family of four on food per month is $500 with a standard
deviation of $75. Assuming a normal distribution, what is the probability that a family spends
more than $410 per month?
A 0.1151
B 0.1539
C 0.8849
D 0.8469
E none of the above
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18. Assume a Normal Distribution with mean µ = 98.7 and IQR = 0.50. Find the standard
deviation.
A 0.37
B 0.25
C 0.50
D 1.50
E none of the above
19. Assume that women’s heights are normally distributed with mean 63.60 inches and standard
deviation 2.50 inches. Find the value for
P90
the 90th percentile.
A 66.10 in
B 66.60 in
C 66.80 in
D 66.83 in
E none of the above
20. The scores on a certain test are normally distributed with mean 61 and standard deviation 3.
What is the probability that a sample of 100 students will have a mean score of at least 61.3?
A 0.4602
B 0.3413
C 0.8413
D 0.1587
E none of the above
21. A random sample of 86 light bulbs had a mean life 545 hours. From other studies it is known
that the population standard deviation of such light bulbs is ? = 29 hours. Construct a 90%
confidence interval for the mean life µ, of all such light bulbs.
A (537.7, 552.3)
B (536.9, 553.1)
C (538.9, 551.1)
D (539.9, 550.1)
E none of the above
22. Thirty randomly selected students took a test. The sample mean was 77 and the sample
standard deviation was s = 5.6. Find the Margin of Error for the 99% confidence interval for the
mean score of all students.
A ME=2.818
B ME=2.634
C ME=2.628
D ME=2.812
E none of the above
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23. A survey of 450 people found that 45 of them had no cell phone. Find the 99% confidence interval of
the true proportion of people who did not have cell phones.
A (0.064, 0.136)
B (0.067, 0.133)
C (0.072, 0.128)
D (0.077, 0.123)
E none of the above
24. Suppose we draw all possible samples of a given size n from a large population that is not
normally distributed. Then the distribution of the samples means will
A be skewed to the right
B be skewed to the left
C be normal
D approach a normal distribution as the sample size n increases.
E none of the above
25. Find t*, the critical t value for a confidence level of 99% and a sample size of 17.
A 2.898
B 2.583
C 2.921
D 2.567
E none of the above
26. The Labor Department wants to estimate the percentage of females in the U.S. labor force.
They select a random sample of 525 employment records, and find that 210 of the people are
females. The Margin of Error for the 90% confidence interval is
A 0.0352
B 0.0419
C 0.0551
D 0.0498
E none of the above
27. If the Department of Labor wishes to tighten its interval, they should
A Increase the confidence level.
B Increase the sample size.
C Decrease the sample size.
D Both A and B
E Both A and C

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