# STAT 200 OL4/US2 Sections Final Exam Fall 2015

August 30, 2017

Question
STAT 200: Introduction to Statistics Final Examination, Fall 2015 OL4/US2 Page 1 of 6
STAT 200
OL4/US2 Sections
Final Exam
Fall 2015
The final exam will be posted at 12:01 am on December 11, and
it is due at 11:59 pm on December 13, 2015. Eastern Time is
our reference time.
This is an open-book exam. You may refer to your text and other course
materials as you work on the exam, and you may use a calculator. You must
complete the exam individually. Neither collaboration nor consultation with
others is allowed.
Answer all 25 questions. Make sure your answers are as complete as possible.
Show all of your work and reasoning. In particular, when there are
calculations involved, you must show how you come up with your answers
with critical work and/or necessary tables. Answers that come straight from
programs or software packages will not be accepted. If you need to use
software (for example, Excel) and /or online or hand-held calculators to aid in
your calculation, please cite the sources and explain how you get the results.
Record your answers and work on the separate answer sheet provided.
This exam has 200 total points.
You must include the Honor Pledge on the title page of your submitted final
exam. Exams submitted without the Honor Pledge will not be accepted.
STAT 200: Introduction to Statistics Final Examination, Fall 2015 OL4/US2 Page 2 of 6
1. True or False. Justify for full credit. (15 pts)
(a) If the variance of a data set is zero, then all the observations in this data set are zero.
(b) If P(A) = 0.4 , P(B) = 0.5, and A and B are disjoint, then P(A AND B) = 0.9.
(c) Assume X follows a continuous distribution which is symmetric about 0. If
, then .
(d) A 95% confidence interval is wider than a 90% confidence interval of the same
parameter.
(e) In a right-tailed test, the value of the test statistic is 1.5. If we know the test statistic
follows a Student’s t-distribution with P(T < 1.5) = 0.96, then we fail to reject the
null hypothesis at 0.05 level of significance .
Refer to the following frequency distribution for Questions 2, 3, 4, and 5. Show all work. Just the
answer, without supporting work, will receive no credit.
The frequency distribution below shows the distribution for checkout time (in minutes) in
UMUC MiniMart between 3:00 and 4:00 PM on a Friday afternoon.
Checkout Time (in minutes) Frequency Relative Frequency
1.0 – 1.9 3
2.0 – 2.9 12
3.0 – 3.9 0.20
4.0 – 4.9 3
5.0 -5.9
Total 25
2. Complete the frequency table with frequency and relative frequency. Express the relative
frequency to two decimal places. (5 pts)
3. What percentage of the checkout times was at least 3 minutes? (3 pts)
4. In what class interval must the median lie? Explain your answer. (5 pts)
5. Does this distribution have positive skew or negative skew? Why? (2 pts)
Refer to the following information for Questions 6 and 7. Show all work. Just the answer,
without supporting work, will receive no credit.
Consider selecting one card at a time from a 52-card deck. (Note: There are 4 aces in a deck of
cards)
6. If the card selection is without replacement, what is the probability that the first card is an ace and
the second card is also an ace? (Express the answer in simplest fraction form) (5 pts)
STAT 200: Introduction to Statistics Final Examination, Fall 2015 OL4/US2 Page 3 of 6
7. If the card selection is with replacement, what is the probability that the first card is an ace and
the second card is also an ace? (Express the answer in simplest fraction form) (5 pts)
Refer to the following situation for Questions 8, 9, and 10.
The five-number summary below shows the grade distribution of two STAT 200 quizzes for
a sample of 500 students.
Minimum Q1 Median Q3 Maximum
Quiz 1 15 30 55 85 100
Quiz 2 20 35 50 90 100
For each question, give your answer as one of the following: (a) Quiz 1; (b) Quiz 2; (c) Both quizzes
have the same value requested; (d) It is impossible to tell using only the given information. Then
explain your answer in each case. (4 pts each)
8. Which quiz has less interquartile range in grade distribution?
9. Which quiz has the greater percentage of students with grades 80 or over?
10. Which quiz has a greater percentage of students with grades less than or equal to 50?
Refer to the following information for Questions 11, 12, and 13. Show all work. Just the answer,
without supporting work, will receive no credit.
There are 1000 students in a high school. Among the 1000 students, 800 students have a
laptop, and 300 students have a tablet. 250 students have both devices.
11. What is the probability that a randomly selected student has neither device? (10 pts)
12. What is the probability that a randomly selected student has a tablet, given that he/she has
a laptop? (5 pts)
13. Let event A be the selected student having a laptop, and event B be the selected student
having a tablet. Are A and B independent events? Why or why not? (5 pts)
14. A combination lock uses three distinctive numbers between 0 and 39 inclusive. How many
different ways can a sequence of three numbers be selected? (Show work) (5 pts)
15. Let random variable x represent the number of heads when a fair coin is tossed three
times. Show all work. Just the answer, without supporting work, will receive no credit.
(a) Construct a table describing the probability distribution. (5 pts)
(b) Determine the mean and standard deviation of x. (Round the answer to two decimal places)
(10 pts)
STAT 200: Introduction to Statistics Final Examination, Fall 2015 OL4/US2 Page 4 of 6
16. Mimi just started her tennis class three weeks ago. On average, she is able to return 25% of her
opponent’s serves. Assume her opponent serves 10 times.
(a) Let X be the number of returns that Mimi gets. As we know, the distribution of X is a binomial
probability distribution. What is the number of trials (n), probability of successes (p) and
probability of failures (q), respectively? (5 pts)
(b) Find the probability that that she returns at least 1 of the 10 serves from her opponent.
(Show work) (10 pts)
Refer to the following information for Questions 17, 18, and 19. Show all work. Just the answer,
without supporting work, will receive no credit.
The lengths of mature jalapeño fruits are normally distributed with a mean of 3 inches and a
standard deviation of 1 inch.
17. What is the probability that a randomly selected mature jalapeño fruit is between 1.5 and 3.5
inches long? (5 pts)
18. Find the 90
th percentile of the jalapeño fruit length distribution. (5 pts)
19. If a random sample of 400 mature jalapeño fruits is selected, what is the standard deviation of the
sample mean? (5 pts)
20. A random sample of 100 light bulbs has a mean lifetime of 3000 hours. Assume that the
population standard deviation of the lifetime is 500 hours. Construct a 90% confidence interval
estimate of the mean lifetime. Show all work. Just the answer, without supporting work, will
receive no credit. (8 pts)
21. Consider the hypothesis test given by
: 0.5
: 0.5
1
0
?
?
H p
H p
In a random sample of 400 subjects, the sample proportion is found to be
p
ˆ
? 0.55.
(a) Determine the test statistic. Show all work; writing the correct test statistic, without
supporting work, will receive no credit.
(b) Determine the P-value for this test. Show all work; writing the correct P-value,
without supporting work, will receive no credit.
(c) Is there sufficient evidence to justify the rejection of
H0
at the
? ? 0.01
level?
Explain. (15 pts)
STAT 200: Introduction to Statistics Final Examination, Fall 2015 OL4/US2 Page 5 of 6
22. Consumption of large amounts of alcohol is known to increase reaction time. To
investigate the effects of small amounts of alcohol, reaction time was recorded for five
individuals before and after the consumption of 2 ounces of alcohol. Do the data below
suggest that consumption of 2 ounces of alcohol increases mean reaction time?
Reaction Time (seconds)
Subject Before After
1 6 7
2 8 8
3 4 6
4 7 9
5 9 8
Assume we want to use a 0.05 significance level to test the claim.
(a) Identify the null hypothesis and the alternative hypothesis.
(b) Determine the test statistic. Show all work; writing the correct test statistic, without
supporting work, will receive no credit.
(c) Determine the P-value. Show all work; writing the correct P-value, without
supporting work, will receive no credit.
(d) Is there sufficient evidence to support the claim that consumption of 2 ounces of
alcohol increases mean reaction time? Justify your conclusion.
(15 pts)
23. The UMUC MiniMart sells five different types of coffee mugs. The manager reports that
the five types are equally popular. Suppose that a sample of 500 purchases yields
observed counts 110, 100, 110, 100, and 80 for types 1, 2, 3, 4, and 5, respectively.
Type 1 2 3 4 5
Number of Mugs 110 100 110 100 80
Assume we want to use a 0.05 significance level to test the claim that the five types are
equally popular.
(a) Identify the null hypothesis and the alternative hypothesis.
(b) Determine the test statistic. Show all work; writing the correct test statistic, without
supporting work, will receive no credit.
(c) Determine the P-value for the test. Show all work; writing the correct P-value,
without supporting work, will receive no credit.
(d) Is there sufficient evidence to support the manager’s claim that the four types are
(15 pts)
STAT 200: Introduction to Statistics Final Examination, Fall 2015 OL4/US2 Page 6 of 6
24. A random sample of 4 professional athletes produced the following data where x is the
number of endorsements the player has and y is the amount of money made (in millions of
dollars).
x 0 1 3 5
y 1 2 5 8
(a) Find an equation of the least squares regression line. Show all work; writing the correct
equation, without supporting work, will receive no credit. (10 pts)
(b) Based on the equation from part (a), what is the predicted value of y if x = 2? Show all
work and justify your answer. (5 pts)
25. A STAT 200 instructor is interested in whether there is any variation in the final exam grades
between her two classes Data collected from the two classes are as follows:

Her null hypothesis and alternative hypothesis are:

(a) Determine the test statistic. Show all work; writing the correct test statistic, without
supporting work, will receive no credit.
(b) Determine the P-value for this test. Show all work; writing the correct P-value, without
supporting work, will receive no credit.
(c) Is there sufficient evidence to justify the rejection of
H0
at the significance level of 0.05?
Explain.
(10 pts)

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