The World Health Organization tracks suicide rates by gender across countries. For example, in 2011, the rate of suicide per 100,000 men was 17.3 in Canada, 17.7 in the United States, 44.6 in Sri Lanka, 53.9 in the Russian Federation, 1.4 in South Africa, and 2.5 in the Philippines. 

a. What are the variables in this study? 

b. Are the variables nominal, ordinal, or scale? 

c. Which graph would be most appropriate to depict the data? Explain why. 

d. If you wanted to track the suicide rates for three of these countries over 50 years, what type of graph might you use to show these data?