b. Heart attack status

c. Depression status

d. Statistic

e. Confounding variable

3.18a. Number of apple per tree.

b. Type of Fertilizer and Soil Moisture status. 

c. Type of fertilizer: 3 levels. Soil moisture: two levels.

d. 3*2*3=18.

3.22The correct answer is (a), treatments are assigned to subjects.

3.30       a. Observational study. Prospective.

b. Explanatory variable: Whole grain food consumption status. Response variable: stroke status.

c. (i)     response bias.

    (ii)    confoundin variable.

3.32        a. (ii)        explanatory variable.

                b. (i)         response variable.

                c. (iv)       a retrospective observational study.

3.34         a. There are 3 explanatory variables: time (3 levels), temperature (3 levels), and cheese (2 levels). So we have 3*3*2=18 treatments.

                b. With 5 batches for each treatment, we have 5*18=90 total units.

3.54         a. Observational study

b. Explanatory variable: Behavioral therapy status.

Response variable: Insomnia status.

c. The number of people in each treatment group is unknown. We only know that they were 75 in total.

d. How were the results analyzed? How were the 75 subjects selected? Was the placebo treatment truly a placebo?
 

#4.58, #4.72 (a, b)
　

4.8

No. The percentages do not add to 100% since people were allowed to check more than one appliance. Since the categories are not disjoint (with a person in one and only category), a pie chart is not an appropriate way to display these data.

4.18

a. Frequency plot for the number of squares for the 20 rats in the experiment.
 

				X	X	X	X
		X		X	X	X	X
X	X	X	X	X	X	X	X	X	X
2	3	4	5	6	7	8	9	10	11

b. The number of squares ranged from 2 up to 11, which most of the rats having values between 6 to 9.
 

4.58
 

a	qualitative
b	quantitative, continuous
c	quantitative, discrete
d	quantitative, continuous
e	quantitative, discrete