Download STAT 211-019 Practice Exam 2 (Choose the answer closest

STAT 211-019 Practice Exam 2
(Choose the answer closest. Answers may vary slightly due to rounding)
1. Find the Expected Value of the following distribution:
1
2
3
4
.1
.35
.35
.2
a.
b.
c.
d.
1.81
2.28
2.65
3.23
2. 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
3. 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
4. Which of the following corresponds to the probability of getting more than 8 successes in a
binomial experiment?
a.
b.
c.
d.
5. Which of the following is not a condition for a binomial experiment?
a. Fixed number of trials, n
b. Constant probability of success, p
c. Each trial consists of 2 outcomes, Success and Failure
d. P(Success) = P(Failure)
6. 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
7. 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
8. 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
9. 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
10. 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
11. 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
12. Which of the following is not a property of every normal distribution?
a. Continuous
b. Symmetric about 0
c. Bell/Mound Shaped
d. Symmetric about
13. X is normally distributed with mean 20 and standard deviation 5. If the P(X<c)=.9192, find c.
a. 27
b. .9192
c. .0808
d. 25
14. 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.
15. 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
16. 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
17. What effect does increasing my sample mean ( ) have on the width of my confidence interval?
a.
b.
c.
d.
Increases the width
Decreases the width
Has no effect on the width
Increases or Decreases the width depending on if the sample mean is positive or
negative
18. 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)
19. 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
20. Suppose I am interested in a 90% confidence interval on , but I can only collect a sample of 9.
The critical value that I will use to calculate the error term will come from
a. A standard Normal Distribution
b. A normal distribution with mean and standard deviation
c. A t distribution with 9 degrees of freedom
d. A t distribution with 8 degrees of freedom
21. A random sample of 225 students was selected and 150 had evidence of poor eating habits.
Find a 95% confidence interval on the true proportion of students who have poor eating habits.
a. (.6051, .7282)
b. (.6149, 7184)
c. (.4281, .9052)
d. (.6626, .6708)
22. Suppose that another sample of 225 students is selected and a confidence interval on the
proportion of students with bad eating habits was performed. The 99% confidence interval
spanned from (.55 to .75). Which of the following statements provides the appropriate
interpretation of the 95% confidence interval?
a. 99% of all students have poor eating habits 55% to 75% of the time
b. We are 99% confident that between 55% and 75% of the sample of 225 students have
poor eating habits
c. We are 99% confident that between 55% and 75% of all students have bad eating
habits
d. We are 95% confident that between 55% and 75% of all students have bad eating habits
23. Farmer Joe is interested in if gender has an influence on whether children like cows. He wants
to calculate a 95% confidence interval for the difference in the population proportion of boy
children who like cows and the proportion of girl children who like cows. Our confidence
interval for
goes from -.06 to .09. Is there statistical evidence for a difference in
proportions?
a. No, because 0 is in the interval
b. No, because 0 is not in the interval
c. Yes, because 0 is in the interval
d. Yes, because 0 is not in the interval
24. I am interested in whether gender has an effect on the mean grade of students for Exam 2. If I
plan on using a confidence interval to answer this question, which type of confidence interval
should I use?
a.
b.
c.
d.
25. A sample generated to predict the difference in population means yields the following summary
data:
. A 99% confidence interval for the
difference in population means
a. Does not require the pooled standard deviation
to be calculated
b. Requires that the critical value come from a standard normal distribution
c. Requires that the critical value come from a t distribution with 33 degrees of freedom
d. Requires that the critical value come from a t distribution with 31 degrees of freedom