Download STAT 211 Practice Exam Exam 1 Use the following Data Set for

STAT 211
Practice Exam
Exam 1
Use the following Data Set for Questions 1 through 4: 11, 21, 33, 12, 8, 14, 27, 11, 13, 1
1. Find the sample mean of the data set
a. 12.5
b. 15.1
c. 14.8
d. 16.3
e. 11.0
2. Find the sample median of the data set
a. 12.5
b. 15.1
c. 14.8
d. 16.3
e. 11.0
3. Find the sample mode of the data set
a. 12.5
b. 15.1
c. 14.8
d. 16.3
e. 11.0
4. Find the sample Inter Quartile Range of the data set
a. 8.00
b. 10.75
c. 6.50
d. 10.00
e. 9.50
5. How are variance and standard deviation related?
a. Variance is ALWAYS the square of the standard deviation
b. Standard Deviation is SOMETIMES the square of the variance
c. Variance is SOMETIMES the square of the variance
d. Standard deviation is ALWAYS the square of the variance
e. There is no exact relation, although they're usually close to one another
6. Randomly roll one 12-sided die. The probability of getting a 4 or 5 is
a. 1/6
b. 2/6
c. 3/6
d. 4/6
e. None of the above
7. The probability that my microphone works is .20. What is the probability that my microphone
does not work.
a. 0
b. .5
c. .80
d. -.80
e. None of the above
Exam 2
1. On a multiple choice exam, there are 4 possible answers to each of 60 questions. What is the
expected number of correct answers if a student guesses on each question?
a. 15
b. 4
c. 1
d. .25
2. 35% of apples purchased at a grocery store contain unhealthy levels of pesticides. A random
sample of 6 apples is obtained. What is the probability that exactly 2 apples have an unhealthy
level of pesticides?
a. .647
b. .353
c. .672
d. .328
3. Which of the following corresponds to the probability of getting more than 8 successes in a
binomial experiment?
a.
b.
c.
d.
4. Assuming you guess on every question, what is the probability of passing your STAT 211 Exam
if there are 20 questions and each question has 5 possible answers? (12 Correct is Passing)
a. .9999
b. .0001
c. .6000
d. .2000
5. Suppose that deer cross a stretch of highway at a rate of 4 per hour. What is the probability that
exactly 6 deer will cross the stretch of highway in one hour?
a. .1107
b. .8893
c. .8958
d. .1042
6. Suppose that deer cross a stretch of highway at a rate of 4 per hour. What is the probability that
between 5 and 8 deer (inclusive) will cross the stretch of highway in one hour?
a. .3498
b. .1935
c. .6502
d. .8065
7. What is the standard deviation of the number of deer who cross the highway stretch in 4 hours?
a. 2
b. 4
c. 8
d. 16
8. The time that it takes to travel from Morgantown to Pittsburgh is normally distributed with a
mean of 1 hour and 30 minutes and a standard deviation of 5 minutes. What is the probability
that a randomly selected car makes it to Pittsburgh in less than 1 hour and 45 minutes?
a. .0014
b. .1587
c. .9987
d. .8413
9. The time that it takes to travel from Morgantown to Pittsburgh is normally distributed with a
mean of 1 hour and 30 minutes and a standard deviation of 5 minutes. What is the probability
that a randomly selected car makes it to Pittsburgh in more than 1 hour and 25 minutes?
a. .0014
b. .1587
c. .9987
d. .8413
10. The average lifespan of a cat is 15 years with a standard deviation of 1 year. Kathryn has a house
filled with 25 cats. What is the mean and standard deviation of the sampling distribution of the
sample mean of cat life spans?
a.
b.
c.
d.
11. The average lifespan of a cat is 16 years with a standard deviation of 1 year. Kathryn has a house
filled with 25 cats. What is the probability that the mean cat lifespan will exceed 16.2 years?
a. .5792
b. .4207
c. .8413
d. .1587
12. Which of the following would result in a decrease in the width of a confidence interval for a
population mean?
a. An decrease in the sample size
b. An increase in the sample size
c. A decrease in the sample mean
d. An increase in the confidence level
e. An increase in the standard error
13. What effect does increasing my sample mean ( ) have on the width of my confidence interval?
a. Increases the width
b. Decreases the width
c. Has no effect on the width
d. Increases or Decreases the width depending on if the sample mean is positive or negative
14. The exam 2 completion time for 25 STAT 211 students has a sample mean of 40 minutes with a
standard deviation of 5 minutes. Compute the 95% confidence interval on the mean completion
time of all STAT 211 students.
a. (39.608, 40.392)
b. (39.922, 40.078)
c. (38.040, 41.960)
d. (38.355, 41.645)
15. Using the Normal Distribution Table, find the area under the normal distribution curve between
Z=-1.63 and Z=2.03
a. .0727
b. .9272
c. .9788
d. .0516
Exam 3
For each of the following scenarios, find the null and alternative hypotheses; compute the appropriate test
statistic; make the appropriate decision and conclusion; note any conditions to use the test:
1. I claim that the average monthly rent cost for a 1 bedroom apartment in Morgantown is more
than $575. A sample of 12 apartments has an average monthly rent cost of $650 and a standard
deviation of $100. At alpha = .05, test my claim.
1.
2.
3. T=
4. Using the T-Table with 11 degrees of freedom, our p-value is between .01 and .02
5. Both of these values are less than .05, reject
6. We have enough evidence at the .05 level to conclude that the average monthly rent cost
for a 1 bedroom apartment in Morgantown is greater than $575.
7. Because our sample size was <20, a t-test is appropriate
2. About 80% of students pass their statistics class on their first attempt. Suppose the department
chair at WVU speculates that this value is less than 80% at WVU. He takes a sample of 250
students at WVU and found 156 of them passed on their first attempt. Use alpha = .10
1.
2.
3. Z=
4. Using the Z table, our p-value is .2389
5. Our p value is > .10, fail to reject
6. We do not have enough evidence at the .10 level to conclude that the proportion of
students who pass their statistics class on their first attempt at WVU is less than 80%.
7. We require that
3. Students were asked, “Would you recommend your English teacher to a student who needs the
class in the future?” Of the 120 students who have had Dr. A in the past, 75% said yes, and of
the 78 students who have had Dr. B in the past, 65% said yes. Do we have enough evidence to
conclude that, for the populations represented by these students, a different proportion of
students of Dr. A’s would answer yes to this question? Use alpha = .10
1.
2.
3. Z=
4. Using the Z table, our p-value is .0681, we must multiply it by 2, so p-value = .1362
5. Our p value is > .10, fail to reject
6. We do not have enough evidence at the .10 level to conclude that a different proportion of
students of Dr. A’s would answer yes to the question.
7. We require that
4.
A student is interested in whether the grade distribution of STAT 211 students follows 10% A’s,
25% B’s, 30% C’s 25% D’s 10% F’s. The student obtains a sample of 66 grades. The observed
counts were 14 A’s, 23 B’s, 15 C’s, 9 D’s, 5 F’s. Test the hypothesis at the .05 level (See Extra
Credit Assignment 2)
1.
2.
3.
4. Using the
table with 4 degrees of freedom, our p-value is between .005 and .0025
5. Both of our p values are <.05, reject
6. We have enough evidence at the .05 level to conclude that the distribution of 10% A’s, 25%
B’s, 30% C’s 25% D’s 10% F’s is not the correct distribution
7. We require that