Researchers studied the 2010 epidemic of pertussis in California. They selected a random sample of 682 medical records of California children ages 4 to 10 who had been diagnosed with pertussis. They also selected a random sample of 2016 medical records of California children in the same age group who had received care from the same clinicians on the same day but were not diagnosed with pertussis.
The study found that children diagnosed with pertussis were much more likely to have not received any pertussis vaccine, to have not received all recommended doses of the vaccine, or to have had a longer interval of time since their last vaccination.
This study is an example of.
a. cross-sectional sample survey
b. longitudinal cohort study
c. case-control observational study
d. completely randomized experiment
e. experiment with matched pairs/repeated measures
f. unscientific study with voluntary sample or anecdotal data
g. census (population data)