# COH 315 COH315 Final Exam Part 2 Answers (National University)

COH 315 Final Exam Part 2 (National University)

Use the information presented in Table 1 to answer Questions 1-7.

* What percentage of cases experienced bloody diarrhea? (2 points)

* What is the median incubation period of this disease? What is the mean incubation period? (Show all work) (2 points)

* Calculate the attack rate in those who ate chicken salad. (Show all work) (2 points)

* Calculate the attack rate for those who did not eat chicken salad. (Show all work) Â (2 points)

â€¢ Calculate the attack rate in those who ate ice cream. (2 points)

â€¢ Calculate the attack rate in those who did not eat ice cream (2 points)

â€¢ Which food is the more likely source of contagion? The chicken salad or the ice cream? (2 points)

A cohort of 800 people begins with 15 prevalent cases. Over the next 2 years, 35 incident cases arise.

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* What is the prevalence of disease at the start of the follow-up period? (Provide numerator and denominator and prevalence the per 1,000 people) (2 points)

* What is the prevalence of the disease at the end of the follow-up period (assume no on is lost to follow-up)? Provide the numerator and denominator. (2 points)

â€¢ What is the cumulative incidence of disease over the follow-up interval? (Provide numerator and denominator, and the cumulative incidence per 1,000 people) (2 points)

A screening test for a preclinical stage of a cancer is known to have a sensitivity of .88 (i.e., 88%) and a specificity of .76 (i.e., 76%). The prevalence of this cancer in its preclinical phase in the population is 8 per 1000 (.008). Assume we use this test in one-hundred thousand (100,000) people. Â Based on this information, determine (12 points):

**Extra Credit**

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In a large urban school district, among 7,500 middle-school school youth who were well at the beginning of the school year, 460 were absent for 10 days or longer due to acute asthma ("AA-10") during the first nine-week quarter. Â Based on a survey believed accurate for the period, 13% of middle-school youth in the county middle schools smoke Â Â Â Â cigarettes. Interviews with the youth who were absent for 10 days or longer revealed that 100 of them were cigarette smokers. Â Assume that the school enrollment does not change during the quarter.

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What is the cumulative incidence (CI) of AA-10 (10+ absent days due to acute asthma), in: Â Â Â Â Â

* the cohort of 7,500 youth? (1 point)