STAT 3321 - Exam 1- White, Spring 2012 - Printed Name______

Ctrl-Click here to go to Blue version. Answer key follows the exam. The relationship between White and Blue questions is here.

1. Suppose the values 12 and 25 cut off the center 90% of the bell-shaped curve. What percentile does the value 12 fall on?

a. none of the other answers are correct

b. 5

c. 10

d. 90

2. What is the mean and median of the following population of numbers? 1, 5, 7, 5, 3, 3, 5, 9, 7?

a. both are the value 5

b. 3 is the median and 5 is the mean

c. 7 is the median and 3 is the mean

d. none of the other answers are correct

3. The sample correlation measures how close values fall from

a. the sample mean

b. a straight line

c. the population mean

d. any type of line (straight or curved)

4. Which formula creates an average by dividing by the sample size minus one?

a. population variance

b. sample variance

c. population mean

d. median

5. The largest error you would expect in a sample mean is called

a. the standard error

b. the margin of error

c. the standard deviation

d. the big error (do not make one by choosing this)

6. You believe that the average starting salary of students depend on their GPA. What would a slope of

$3000 indicate?

a. When the GPA is zero, the average starting salary is estimated to be $3000

b. The average starting salary is $3000.

c. For each one point increase in GPA, the mean starting salary is estimated to increase by $3000.

d. The slope is the average GPA when the starting salaries increase by $3000

7. If Pr(A) = 0.40 and Pr(B)=0.70, then all you know for sure is that

a. nothing is known for sure.

b. A and B are independent

c. A and B are not mutually exclusive

d. A and B are mutually exclusive

8. You are answering a test with 25 questions and you believe that you have a 70% chance of getting any one correct. What is the probability of getting 20 correct? Choose the appropriate substitution.

b. none of the other answers are correct

9. Given the table on the right, find the Pr (A1|B2)

A1 / A2 / A3
B1 / 0.03 / 0.41 / 0.06
B2 / 0.17 / 0.19 / 0.14

a. 0.34

b. 0.59

c. 0.17

d. none of the other answers are correct

10. If Pr(A) = 0.3, Pr (B) = 0.70, and Pr(A | B) = 0.2, then what is the probability of A and B?

a. 1.00

b. none of the other answers are correct.

c. 0.14

d. 0.80

11. Suppose a population follows the bell-shaped distribution with =$75489 and =$112, what is the probability that you will find a value within $112 of the population mean?

a. none of the other answers are correct

b. 100%

c. 95%

d. 68%

12. A tax district is trying to determine the average amount of error in neighborhood appraised values.The first step is to check for typing or recording errors. In this step they are looking for:

a. sampling error

b. non-sampling errors

c. statistical knowledge of their household (hint: seems like a good idea but bad choice for an answer here.)

d. none of the other answers are correct.

13. When can I say that there is a 95% probability that the next value under a bell-curve falls within two standard deviations of the mean?

a. when calculating a mean

b. always

c. under random sampling

d. in pie charts

14. The symbol  represents

a. the population standard deviation

b. the population slope

c. the sample standard deviation

d. the sample slope

15. Which of the following is a measure of variability?

a. oven

b. range

c. microwave

d. camp fire

16. I will ask a question of the first 20 people to leave a polling station. This is an example of a(n) ….

a. experiments

b. convenience sampling

c. random sampling

d. correlation

17. Suppose you have a binomial with n=1,600 and p=0.20. Assuming the distribution of the counts is mound-shaped symmetric, what is the value of x on the 84th percentile?

a. 320

b. 338

c. none of the other answers are correct

d. 304

18. In both a bar chart and a histogram one of the axes is the count of values within categories. For the other axis the histogram’s categories correspond to

a. percentages.

b. random samples

c. ranges.

d. pie slices.

19. To identify a problem that needs to be answered using a binomial you would look for a question that asks:

a. What is the shape of the pie chart?

b. What is the probability of a sample variance?

c. What is the value of the sample variance?

d. What is the probability of a certain number of successes?

20. A standard error in a sample mean consists of

a. a random sample

b. means and variance

c. nothing really important (Hint: BAD, BAD CHOICE)

d. variability and knowledge

21. If you can use the empirical rule, then you would expect that

a. mean would equal the median.

b. the mean would be to the right of the median

c. the standard deviation would be small

d. the correlation would be larger than 1

22. An ogive (cumulative percentage polygon) is used to graph

a. means

b. percentiles

c. relationship between two different variables such as sales and assets

d. qualitative data

23. Which of the following is used to obtain side-by-side bar charts?

a. correlation

b. mean

c. variance

d. pivot table

24. Given n=20 and p=0.1, find Pr(x≤6).

a. 0.998

b. 0.002

c. 0.989

d. none of the other answers are correct.

25. Among the 10,000 students at a college 18% use Facebook. Of the students that use Facebook, 79% use Twitter. While among those students that do not use Facebook, 74% use Twitter. Given that a randomly selected student uses Twitter, what is the probability that the student does use Facebook?

a. 0.14

b. 0.625

c. 0.19

d. none of the other answers are correct.

#Key

10C

11D

12B

13C but B accepted

14B

15B

16B

17C

18C

19D

20D

21A

22B

23D

24A

25C

Relationship between White and Blue Questions

BlueWhite

121

232

134

195

106

227

210

2011

412

1613

1114

1815

2516

617

1418

919

2420

721

2122

1523

324

1725

BSTAT 3321 - Exam 1- Blue, Spring, 2012 - Printed Name______

1. The sample correlation measures how close values fall to

a. the population mean

b. any type of line (straight or curved)

c. the sample mean

d. a straight line

2. If Pr(A) = 0.3, Pr (B) = 0.70, and Pr(A | B) = 0.2, then what is the probability of A and B?

a. 0.14

b. 0.06

c. 1.00

d. none of the other answers are correct.

3. Given n=20 and p=0.1, find Pr(x≤6).

a. 0.989

b. none of the other answers are correct.

c. 0.998

d. 0.002

4. A tax district is trying to determine the average amount of error in the appraised values of houses in a city.The first step is to check for typing or recording errors. In this step they are looking for:

a. statistical knowledge of their household (hint: seems like a good idea but bad choice for an answer here.)

b. none of the other answers are correct.

c. sampling error

d. non-sampling errors

5. Given the table on the right, find the Pr (A1|B2)

A1 / A2 / A3
B1 / 0.03 / 0.41 / 0.06
B2 / 0.17 / 0.19 / 0.14

a. 0.17

b. none of the other answers are correct

c. 0.34

d. 0.59

6. Suppose you have a binomial with n=1,600 and p=0.20. Assuming the distribution of the counts is mound-shaped symmetric, what is the value of x on the 84th percentile?

a. none of the other answers are correct

b. 304

c. 320

d. 338

7.If you can use the empirical rule, then you would expect that

a. the standard deviation would be small

b. the correlation would be larger than 1

c. the mean would equal the median.

d. the mean would be to the right of the median

d. none of the other answers are correct

9. To identify a problem that needs to be answered using a binomial you would look for a question that asks:

a. What is the value of the sample variance?

b. What is the probability of a certain number of successes?

c. What is the shape of the pie chart?

d. What is the probability of a sample variance?

10. You believe that the average starting salary of students depend on their GPA. What would a slope of

$3000 indicate?

a. For each one point increase in GPA, the mean starting salary is estimated to increase by $3000.

b. The slope is the average GPA when the starting salaries increase by $3000

c. When the GPA is zero, the average starting salary is estimated to be $3000

d. The average starting salary is $3000.

11. The symbol  represents

a. the sample standard deviation

b. the sample slope

c. the population standard deviation

d. the population slope

12. Suppose the values 12 and 25 cut off the center 90% of the bell-shaped curve. What percentile does the value 12 fall on?

a. 10

b. 90

c. none of the other answers are correct

d. 5

13. Which formula creates an average by dividing a sum by the sample size minus one?

a. population mean

b. median

c. population variance

d. sample variance

14. In both a bar chart and a histogram one of the axes is the count of values within categories. For the other axis the histogram’s categories correspond to

a. ranges of values.

b. pie slices.

c. percentages.

d. random samples

15. Which of the following is used to obtain side-by-side bar charts?

a. variance

b. contingency table

c. correlation

d. mean

16. When can I say that there is a 95% probability that the next value under a bell-curve falls within two standard deviations of the mean?

a. under random sampling

b. in pie charts

c. when calculating a mean

d. always

17. Among the 10,000 students at a college 18% use Facebook. Of the students that use Facebook, 79% use Twitter. While among those students that do not use Facebook, 74% use Twitter. Given that a randomly selected student uses Twitter, what is the probability that the student does use Facebook?

a. 0.19

b. none of the other answers are correct.

c. 0.14

d. 0.625

18. Which of the following is a measure of variability?

a. microwave

b. camp fire

c. oven

d. range

19. With a specified probability, what is another name for the largest error you would expect in a sample mean?

a. the standard deviation

b. the big error (do not make one by choosing this)

c. the standard error

d. the margin of error

20. Suppose a population follows the bell-shaped distribution with =$75489 and =$112, what is the probability that you will find a value within $112 of the population mean?

a. 95%

b. 68%

c. none of the other answers are correct

d. 100%

21. An ogive (cumulative percentage polygon) is used to graph

a. the relationship between two different variables such as sales and assets

b. qualitative data

c. means

d. percentiles

22. If Pr(A) = 0.40 and Pr(B)=0.70, then all you know for sure is that

a. A and B are not mutually exclusive

b. A and B are mutually exclusive

c. nothing is known for sure.

d. A and B are independent

23. What is the mean and median of the following population of numbers? 1, 5, 7, 5, 3, 3, 5, 9, 7?

a. 7 is the median and 3 is the mean

b. none of the other answers are correct

c. both are the value 5

d. 3 is the median and 5 is the mean

24. A standard error in a sample mean consists measures of

a. nothing really important (Hint: BAD, BAD CHOICE)

b. variability and knowledge

c. a random sample

d. means and variance

25. Suppose during an election a pollster will ask a question of the first 20 people to leave a polling station. This is an example of a(n) ….

a. random sampling

b. correlation

c. experiments

d. convenience sampling

#Key

10A

11D

12D

13D

14A

15B

16A

17A

18D

19D

20B

21D

22A

23C

24B

25D