A study was done to determine whether the amount of money spent on soft drinks was related to mortality from diabetes. The investigators collected data on per capita (average per person) soft drink consumption in ten US states and examined its relationship to mortality rates from diabetes in those ten states. In order to calculate per capita sales, they gathered annual data on soft drink sales from commerce records and then divided these figures by the state’s population from the most recent census. The mortality data were gathered from the vital records department in each state. Here are the data that they collected.

US State Annual per Capita- Annual Diabetes Mortality
Soft Drink Sales Rate (per 100,000 population)
Massachusetts $150 207
New York $300 353
Florida $500 688
Alabama $700 801
Alaska $50 75
California $500 605
Nevada $200 310
Idaho $250 325
Ohio $400 454
Arkansas $350 405

(a) What type of study is this? Give a justification for your answer. Hint: Do not select cross-sectional.
(b) Based on these findings, the investigators concluded that there was an association between consumption of soft drinks and mortality from diabetes. Do you agree or disagree with this conclusion?
(c) Unfortunately, the investigators had never taken an epidemiology course and did not acknowledge any limitations of their study. Briefly describe two major limitations that they should have acknowledged.