1.   What does it mean for a sample to be truly random, according to our notes?

a.   Every individual in the sample has the same chance of being selected.

b.   Every sample of the same size has the same chance of being selected.

c.   Every individual in the population has the same chance of being selected.

d.  None of the above.

2.   A confidential survey is one in which they cannot link you to your data.

a.   True                b. False

3.   A confounding variable can cause the results of a two-way table to reverse when it is added to the data set.

a.   True                b. False

4.   Which measure of variability measures the concentration of the data around the mean?

a.   The IQR

b.   The standard deviation

c.   The correlation

d.   All of the above

5.   There can be different amounts of data in each section of a boxplot.

a.   True                b. False

6.   IQR is affected by outliers.

a.   True                b. False

7.   The equation of a regression line is Y = 20 + 5X where X = hours studied and Y = exam score. Study time data ranged from 8 to 15 hours. Should we interpret the Y-intercept    here?

a.   Yes. If someone studies 0 hours, they are expected to get 20 points.

b.  No. You should not interpret the Y-intercept in this situation.

c.   Not enough information to tell.

8.   SSE is equal to what?

a.   The Sum of Squares for Error for any line going through the data.

b.   The Sum of Squares for Error for only the best line going through the data.

9.   If r = -.7, what is the value of the coefficient of determination?

a.   -.49

b.   .49

c.   .70

d.   -.70

e.   None of these / not enough information to tell.

10. Which type of probabilities are in each of the 4 cells of a two-way table of probabilities?

a.   Conditional probabilities

b.   “And” probabilities

c.   Marginal probabilities

d.  None of the above

11. If there is no relationship between two variables in a two-way table, then the two variables are said to be:

a.   Independent

b.   Dependent (also known as Not Independent)

c.   Not enough information to tell.

12. If you are predicting gas price using temperature, which is the X variable?

a.   Gas price

b.   Temperature

c.   Cannot tell without more information

13. If you add the same value to every single number in a data set, the standard deviation also changes by that same value.

a.   True                      b. False

14. If you multiply every single number in a data set by the same value, the standard deviation is also multiplied by that same value.

a.   True                      b. False

15. Which of the following is NOT in the same units as the original data?

a. standard deviation

b. Q1

c. y-intercept of the regression line

d. All of the above are in the same units as the original data.

16. Bob collected data to compare years of education and hours watching TV in the last        month, to see if a relationship exists. His computer output is shown below. Based on this information, is there a strong linear relationship?

a.   Yes

b.  No

c.   Can’t tell with the information given

17. Data Sets #1 and #2 each contain 20 values. Which Data Set has the highest standard deviation according to the histograms below?

a.  Data Set #1            b. Data Set #2

18. A and Ac are disjoint events.  (Hint: what does it mean for events to be disjoint?)

a.   True                                        b. False

19. If A and B are independent events with P(A) = 0.20 and P(B) = 0.60, then P(A|B) is:

a.   0.20

b.   0.60

c.   0.12

d.   None of the above / Can’t tell without more information.

20. Suppose that the price (in $thousands) and size (in square feet) of a random sample of houses in Viroqua, Wisconsin was analyzed by a new statistician; the output is below. The group plans to use the data to help set prices for homes based on their size.

Using this regression line from the output above, which of the following is true?

a.   As size of house increases by 1 square foot, price increases by .15556 thousand dollars (that is, $155.56).

b.   As size of house increases by 1 square foot, price decreases by $90.88.

c.   As the price increases by 1 (thousand $) the size increases by .1556 sq. ft.

d.   As the price increases by 1 (thousand $) the size increases by 52.62 sq. ft.

21. The correlation between study time for an exam (in minutes) and exam score is 0.79. If we convert study time to hours, the correlation will

a.   Increase by a factor of 60

b.   Decrease by a factor of 60

c.   Switch signs to become -0.79

d.   Stay the same

22. If you switch X and Y, which of the following will change?

a.   The correlation

b.   The slope of the regression line

c.   The Y-intercept of the regression line

d.   Both b and c will change

e.   All of a, b, and c will change

23. Which of the following statistics can NEVER be negative?

a.   Correlation

b.   Slope of the regression line

c.   Y-intercept of the regression line

d.   All of the above can be negative, if the data permits.

24. If P(A) = .2, P(B) = .3, and P(A|B) = . 1, what is P(A and B)?

a.   .06

b.   .1

c.   .02

d.   .03

e.   None of the above

25.  If the correlation is 0 you know there is no relationship between X and Y.

a.   True                      b. False

26. A recent Maryland highway safety study looked at two variables involving highway        accidents: 1) whether the driver was wearing a seat belt; and 2) whether the driver           avoided serious injury. They found that: 1) 77% of the time the driver was wearing a seat belt; 2) 92% of the drivers who were wearing a seat belt avoided serious injury, and 3)    63% of the drivers who didn’t wear a seat belt avoided serious injury. Find the total         percentage of drivers who avoided serious injury. Show work and notation for full credit.

27. Previous problem, continued. Suppose a driver escaped serious injury. What is the

chance they were wearing a seat belt? Show all work and notation for full credit.

28. Suppose the regression line for X and Y is y = 2x+1 and the data points are (1, 3); (1, 4); (2, 3); and (3, 6). What is the SSE for this line? (Hint: Another name for Error is        Residual.)  You should get one number in the end. Show all work.

29. Consider the following 2x2 table of probabilities. Find the marginal distribution of gender.

Opinion

30. Bob is a telemarketer and he makes a sale 20% of the time. Suppose he makes ten calls. What is the chance he makes AT LEAST ONE sale?  Show your work.