a. The mean age of six people in a room is 27 years. One of the people whose age is 47 years leaves the room. What is the mean age of the remaining five people in the room?

26 years, 23 years, 20 years or cannot be determined from the information

b. You fit a regression and the R² = 0.9. Check the box next to all the statements that are TRUE.

- 90% of the variability in y is explained by the regression of y on x (beyond what is explained by the mean of y).

- x and y are positively, strongly correlated.

- If the regression were reversed (x as the response and y as the explanatory variable), R2 would equal -0.9.

- The ratio of SSerr to SStot = 0.9.

c. True or False: Correlation measures how much a change in the explanatory variable causes a change in the response variable.

d. True of False: The correlation is a unitless measure of association.

e. True of False: Correlation measures the strength of the linear association between two categorical variables.

f. Switchgrass is a renewable energy source, and its biomass (tons/ac) production from fields in a certain region followed a normal distribution as N(25, 9). What is the proportion of fields producing between 30 tons/ac and 35 tons/ac of switchgrass biomass? (show answer in decimal form)

g. College students were given an "environmental awareness" survey, with 0 implying complete ignorance and 5 suggesting full awareness. The survey results are below:

4.90 ,4.32, 3.12, 2.98, 2.97, 2.94, 1.98, 1.71, 1.54

The first, second, and third quartiles are 1.98, 2.97, and 3.12, respectively. Given this information, check all the observations that may be potential outliers.

1.54

1.71

1.98

2.94

2.97

2.98

3.12

4.32

4.90

h. You fit a regression, resulting in y = -1.7 + 2.3x. If the variance of the residuals = 3.8, calculate the standardized residual when x = 1 and y = 8.

Is this standardized residual extreme?

Yes

No

It depends, on sample size

It depends, on the units of the response

i. True or False: The median is larger than the mean in left skewed distributions.

j. True of False: The median is a resistant measure of spread.

k. You fit a regression of fish weight (response, in lbs) on fish length (explanatory, in inches). Your resulting equation is y = -1.21 + 1.734x. What are the units on the slope coefficient?

* -1.21

* 173.4%

* lbs

* lbs/inches

* inches

* inches/lbs