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)  (2 points)

• Calculate the attack rate in those who ate ice cream. (2 points)

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

• 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.

* 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)

• 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.  Based on this information, determine (12 points):

Extra Credit

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.  Based on a survey believed accurate for the period, 13% of middle-school youth in the county middle schools smoke         cigarettes. Interviews with the youth who were absent for 10 days or longer revealed that 100 of them were cigarette smokers.  Assume that the school enrollment does not change during the quarter.

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

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