20. The graph on the final page of this document shows the current average asthma prevalence by age group, sex, race/ethnicity, household poverty status, geographic region, and urbanicity for the period 2008-2010. This data was based on a household telephone survey conducted on random samples of households in each of the 50 states in the United States.

a. Based on this data alone, what was the specific design of this study? Be as specific as possible. (1 point)

b. Please comment on/describe the patterns for any two of the characteristics shown in the graph.

c. For any one of the characteristics you commented on in part b, please propose and briefly describe one hypothesis that could possibly explain the differences/patterns that you observed.