CHAPTER 5 & CHAPTER 6
1. Thirty-six of the staff of 80 teachers at a local intermediate school are certified in
Cardio-Pulmonary Resuscitation (CPR). In 180 days of school, about how many days
can we expect that the teacher on bus duty will likely be certified in CPR?
a) 5 days
b) 45 days
c) 65 days
d) 81 days
2. A probability distribution is an equation that
a) associates a particular probability of occurrence with each outcome in the
sample space.
b) measures outcomes and assigns values of X to the simple events.
c) assigns a value to the variability in the sample space.
d) assigns a value to the center of the sample space.
3. The connotation "expected value" or "expected gain" from playing roulette at a casino
means
a) the amount you expect to "gain" on a single play.
b) the amount you expect to "gain" in the long run over many plays.
c) the amount you need to "break even" over many plays.
d) the amount you should expect to gain if you are lucky.
4. Which of the following about the binomial distribution is not a true statement?
a) The probability of event of interest must be constant from trial to trial.
b) Each outcome is independent of the other.
c) Each outcome may be classified as either "event of interest" or "not event of
interest."
d) The random variable of interest is continuous.
5. In a binomial distribution
a) the random variable X is continuous.
b) the probability of event of interest  is stable from trial to trial.
c) the number of trials n must be at least 30.
d) the results of one trial are dependent on the results of the other trials.
6.
Whenever p = 0.5, the binomial distribution will
a) always be symmetric.
b) be symmetric only if n is large.
c) be right-skewed.
d) be left-skewed.
7. Whenever p = 0.1 and n is small, the binomial distribution will be
a) symmetric.
b) right-skewed.
c) left-skewed.
d) None of the above.
8. If n = 10 and p = 0.70, then the mean of the binomial distribution is
1
a)
b)
c)
d)
0.07
1.45.
7.00
14.29
9. If n = 10 and p = 0.70, then the standard deviation of the binomial distribution is
a) 0.07
b) 1.45
c) 7.00
d) 14.29
10. If the outcomes of a random variable follow a Poisson distribution, then their
a) mean equals the standard deviation.
b) median equals the standard deviation.
c) mean equals the variance.
d) median equals the variance.
11. What type of probability distribution will most likely be used to analyze the number
of chocolate chip parts per cookie in the following problem?
The quality control manager of Marilyn’s Cookies is inspecting a batch of
chocolate chip cookies. When the production process is in control, the average
number of chocolate chip parts per cookie is 6.0. The manager is interested in
analyzing the probability that any particular cookie being inspected has fewer
than 5.0 chip parts.
a) binomial distribution.
b) Poisson distribution.
c) normal distribution.
d) none of the above.
12. A professor receives, on average, 24.7 e-mails from students the day before the
midterm exam. To compute the probability of receiving at least 10 e-mails on such
a day, he will use what type of probability distribution?
a) binomial distribution.
b) Poisson distribution.
c) normal distribution.
d) none of the above.
13. A company has 125 personal computers. The probability that any one of them will
require repair on a given day is 0.025. To find the probability that exactly 20 of the
computers will require repair on a given day, one will use what type of probability
distribution?
a) binomial distribution.
b) Poisson distribution.
c) normal distribution.
d) none of the above.
14. On the average, 1.8 customers per minute arrive at any one of the checkout counters
of a grocery store. What type of probability distribution can be used to find out the
probability that there will be no customer arriving at a checkout counter?
a) binomial distribution.
b) Poisson distribution.
c) normal distribution.
d) none of the above.
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15. A multiple-choice test has 30 questions. There are 4 choices for each question. A
student who has not studied for the test decides to answer all questions randomly.
What type of probability distribution can be used to figure out his chance of getting at
least 20 questions right?
a) binomial distribution.
b) Poisson distribution.
c) normal distribution.
d) none of the above.
16. A lab orders 100 rats a week for each of the 52 weeks in the year for experiments that
the lab conducts. Suppose the mean cost of rats used in lab experiments turned out to
be $13.00 per week. Interpret this value.
a) Most of the weeks resulted in rat costs of $13.00.
b) The median cost for the distribution of rat costs is $13.00.
c) The expected or average cost for all weekly rat purchases is $13.00.
d) The rat cost that occurs more often than any other is $13.00.
17. A lab orders 100 rats a week for each of the 52 weeks in the year for experiments that
the lab conducts. Prices for 100 rats follow the following distribution:
Price:
$10.00
$12.50
$15.00
Probability:
0.35
0.40
0.25
How much should the lab budget for next year’s rat orders be, assuming this
distribution does not change?
a) $520
b) $637
c) $650
d) $780
18. The local police department must write, on average, 5 tickets a day to keep
department revenues at budgeted levels. Suppose the number of tickets written per
day follows a Poisson distribution with a mean of 6.5 tickets per day. Interpret the
value of the mean.
a) The number of tickets that is written most often is 6.5 tickets per day.
b) Half of the days have less than 6.5 tickets written and half of the days have
more than 6.5 tickets written.
c) If we sampled all days, the arithmetic average or expected number of tickets
written would be 6.5 tickets per day.
d) The mean has no interpretation since 0.5 ticket can never be written.
19. In its standardized form, the normal distribution
a) has a mean of 0 and a standard deviation of 1.
b) has a mean of 1 and a variance of 0.
c) has an area equal to 0.5.
d) cannot be used to approximate discrete probability distributions.
20. Which of the following about the normal distribution is not true?
a) Theoretically, the mean, median, and mode are the same.
b) About 2/3 of the observations fall within  1 standard deviation from the
mean.
c) It is a discrete probability distribution.
d) Its parameters are the mean,  , and standard deviation,  .
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21. If a particular batch of data is approximately normally distributed, we would find that
approximately
a) 2 of every 3 observations would fall between  1 standard deviation around
the mean.
b) 4 of every 5 observations would fall between  1.28 standard deviations
around the mean.
c) 19 of every 20 observations would fall between  2 standard deviations
around the mean.
d) All the above.
22. For some positive value of Z, the probability that a standard normal variable is
between 0 and Z is 0.3770. The value of Z is
a) 0.18
b) 0.81
c) 1.16
d) 1.47
23. For some value of Z, the probability that a standard normal variable is below Z is
0.2090. The value of Z is
a) 0.81
b) 0.31
c) 0.31
d) 1.96
24. For some positive value of Z, the probability that a standard normal variable is
between 0 and Z is 0.3340. The value of Z is
a) 0.07
b) 0.37
c) 0.97
d) 1.06
25. If we know that the length of time it takes a college student to find a parking spot in
the library parking lot follows a normal distribution with a mean of 3.5 minutes and a
standard deviation of 1 minute, find the probability that a randomly selected college
student will find a parking spot in the library parking lot in less than 3 minutes.
a) 0.3551
b) 0.3085
c) 0.2674
d) 0.1915
26. If we know that the length of time it takes a college student to find a parking spot in
the library parking lot follows a normal distribution with a mean of 3.5 minutes and a
standard deviation of 1 minute, find the probability that a randomly selected college
student will take between 2 and 4.5 minutes to find a parking spot in the library parking
lot.
a) 0.0919
b) 0.2255
c) 0.4938
d) 0.7745
27. If we know that the length of time it takes a college student to find a parking spot in
the library parking lot follows a normal distribution with a mean of 3.5 minutes and a
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standard deviation of 1 minute, find the point in the distribution in which 75.8% of the
college students exceed when trying to find a parking spot in the library parking lot.
a) 2.8 minutes
b) 3.2 minutes
c) 3.4 minutes
d) 4.2 minutes
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