Volume 22, Number 7—July 2016
Research
Comparing Characteristics of Sporadic and Outbreak-Associated Foodborne Illnesses, United States, 2004–2011
Figure 3
![Residual plots relative to fitted estimates of outbreak-associated case frequency for the best-fitting models used in the analysis of Foodborne Diseases Active Surveillance Network (FoodNet) data, United States, 2004–2011. A) Campylobacter; B) Escherichia coli O157; C) Listeria; D) Salmonella. Generally, all 4 pathogen models demonstrate reasonable fit because the studentized residuals ([observed frequency – predicted frequency of outbreak-associated cases]/SE of predicted frequency) are mostly](/eid/images/15-0833-F3.jpg)
Figure 3. Residual plots relative to fitted estimates of outbreak-associated case frequency for the best-fitting models used in the analysis of Foodborne Diseases Active Surveillance Network (FoodNet) data, United States, 2004–2011. A) Campylobacter; B) Escherichia coli O157; C) Listeria; D) Salmonella. Generally, all 4 pathogen models demonstrate reasonable fit because the studentized residuals ([observed frequency – predicted frequency of outbreak-associated cases]/SE of predicted frequency) are mostly within 3 SD of the predicted mean frequency of outbreak-associated cases. The state variable is the only factor in the Campylobacter model, whereas year is included in the E. coli O157 and Listeria models. The Salmonella model includes state, year, season, age, and interaction terms.