Scenario

ACME, a manufacturing company in Morgan County, Georgia, hosted its annual company picnic on May 5, 2012. Friends and family members of employees were also invited. Between 250 and 300 people attended the event.

Catering services were provided by a local sandwich shop. The following sandwiches were listed as menu items:

?Peanut butter and jelly

?Reuben

?Egg salad

?Ham and cheese

?Grilled chicken

?Grilled cheese

Salads were offered with each meal:

?Caesar salad

?Garden salad

?Chef salad

Optional snacks or sides:

?Potato chips

?Freshly baked chocolate chip cookies

?Freshly baked peanut butter cookies

Choice of drinks:

?Water

?Iced tea

Because the event had many attendees, food was served at two different times (noon and 2:00 p.m.) to give the shop ample opportunity to make all the dishes.

Over the days following the picnic, the county health department became inundated with calls and faxed lab reports of several culture-confirmed Salmonella enteritidis cases. Most cases were associated with the ACME company picnic held on May 5. Because there was a sudden increase in Salmonella cases over the weekend, an investigation into a potential outbreak was conducted. A roster of attendees at the picnic was obtained and each person was contacted. A case was defined as any attendee who attended the ACME company picnic and developed diarrhea, abdominal cramps, and/or fever after 72 hours of the picnic. A total of at least 90 cases met the case definition.

QUESTIONS

1. Conduct logistic regression analysis to determine whether age was positively associated with the Salmonella outbreak. Provide the Risk Ratio (RR), Odds Ratio (OR), Confidence Intervals (CI), corrected Chi Square, and corrected p-values generated from your analysis and discuss whether any age group was positively associated with the Salmonella outbreak. Use p-value (? 0.05).

2.Conduct a logistic regression (outcome variable = ill) and (independent variable = foods eaten at the picnic). Which were the top three foods with the highest odds ratio associated with becoming ill?

a.Provide the Odds Ratio (OR), Confidence Intervals (CI), and p-values generated from your analysis of these foods. Use p-value (? 0.05).

b.Interpret your findings from item 2a above. (2 points)

c.From the data analysis results, discuss whether any foods were positively associated with the Salmonella outbreak at the ACME company picnic. (2 points)

Logistic Regression OF A X Term Odds Ratio 95% C.I. Coefficient S.E. Z-Statistic | P-Value AGE1 0.9501 0.8603 1.0492 -0.0512 0.0507 -1.0111 0.3120 AGE_GROUPS (10 - 1.0E12 15.1391 384.8985 0.0393 0.9686 AGE_GROUPS (66 - 1.0812 15.3433 544.4962 0.0282 0.9775 CONSTANT 1.3306 1.1782 1.1294 0.2587 Convergence: Converged Iterations: 13 Final -2*Log-Likelihood: 386.5894 Cases Included: 309 Test Statistic D.F. P-Value Score 20.1892 8 0.0096 Likelihood Ratio 22.3842 8 0.0043Logistic Regression Term Odds Ratio 95% C.I. Coefficient S.E. Z-Statistic P-Value PBJ (True/False) 1.5743 0.7733 3.2050 0.4538 0.3627 1.2512 0.2108 Reuben (True/False) 1.3248 0.6697 2.6205 0.2812 0.3480 0.8080 0.4191 HamCheese (True/False) 0.5903 0.2526 1.3796 -0.5271 0.4331 -1.2169 0.2236 GrilledCheese (True/False) 1.5816 0.8060 3.1036 0.4584 0.3439 1.3328 0.1826 GrilledChickenSandwich (True/False) 1.2725 0.6935 2.3352 0.2410 0.3097 0.7781 0.4365 CaesarSalad (True/False) 1.8845 0.9845 3.6075 0.6337 0.3313 1.9128 0.0558 GardenSalad (True/False) 1.4490 0.7257 2.8932 0.3708 0.3528 1.0511 0.2932 ChefSalad (True/False) 4.1392 1.9866 8.6240 1.4205 0.3745 3.7928 0.0001 PotatoChips (True/False) 1.0411 0.6271 1.7285 0.0403 0.2587 0.1557 0.8763 ChocolateChipCookies (True/False) 0.7623 0.4537 1.2808 -0.2715 0.2648 -1.0253 0.3052 PeanutButterCookies (True/False) 0.6290 0.3516 1.1251 -0.4637 0.2967 -1.5627 0.1181 EggSaladSandwich (True/False) 3.4156 1.7828 6.5440 1.2284 0.3317 3.7028 0.0002 CONSTANT -1.2768 0.5028 -2.5395 0.0111 Convergence: Converged Iterations: Final -2*Log-Likelihood: 380.1788 Cases Included: 309 Test Statistic D.F. P-Value Score 27.2163 0.0072 Likelihood Ratio 28.7948 12 0.0042