While many consider the ecological study design methodologically inferior to the cohort and case control designs, this exercise will highlight some of its unique strengths (in addition to key limitations). Please see Aschengrau & Seage, pp. 160-164 for more information.
Good luck and have fun!
Faculty Highlight: Pam R. Factor-Litvak, PhD
Dr. Pam Factor-Litvak's current research interests concern the biological relationships between environmental exposures and development. She has recently completed two studies initiated due to public concerns: the first is a study of the possible associations between mercury derived from dental restorations (silver-mercury fillings) and neuropsychological, neurological and psychiatric symptoms in adults; and the second is an ecological study of the relationship between residential proximity to hazardous waste sites and autism identified from the rosters of special education programs of school districts.
Read more about Dr. Factor-Litvak's work in the following article:
Graziano J, Slavkovich V, Liu X, Factor-Litvak P, Todd A: A prospective study of prenatal and childhood lead exposure and erythropoietin production. Journal of Occupational and Environmental Medicine 46:924-929, 2004.
"There are times when ecological studies may be more appropriate than other designs; for example, when studying the impact of an exposure (or a prevention program) on a community level. Those who only preach the ecological bias do not fully understand the public health usefulness of this design. There are biases, for sure, but no more or less than other designs. Just be sure to make your inferences to the unit of analysis."