Suppose in our Biostatistics 310 class of 120 students where no students had the
ID: 3201770 • Letter: S
Question
Suppose in our Biostatistics 310 class of 120 students where no students had the flu when the winter quarter started, 2 students got the flu at the end of the first week, 4 got the flu at end of the second week, and 8 got the flu at the end of the third week. Five students dropped the class at the end of the fourth week and we don't know whether or not they got the flu by the end of the quarter. The remaining students did not get the flu during the quarter. For the purpose of this problem, assume there are 10 full weeks in the winter quarter and that the strain of flu is so bad that once a student gets the flu, they still have it at the end of the quarter. a) Calculate the incidence rate for the flu in our Biostatistics 310 population. b) Can you calculate the 1 week cumulative incidence of the flu in our Biostatistics 310 population? If so, what is it? (By 1 week, we mean end of 1 week.) If not, why not? c) Can you calculate the 3 week cumulative incidence of the flu in our Biostatistics 310 population? If so, what is it? (By 3 week, we mean end of 3 weeks.) If not, why not? d) Can you calculate the 10 week cumulative incidence of the flu in our Biostatistics 310 population? If so, what is it? (By 10 week, we mean end of 10 weeks.) If not, why not? e) Suppose the reason the 5 students dropped the class was because they were starting to feel sick. How might this affect your interpretation of the incidence rate in part a). f) What is the prevalence of the flu at the beginning of the quarter in our Biostatistics 310 population?Explanation / Answer
a) Incidence rate for the flu = 19/120 = 0.16%
b) 1 week cumulative incidence of flu = 2/120 = 0.02%
c) 3 week cumulative incidence of flu = 14/120 = 0.12%
d) 10 week cumulative incidence of flu = overall incidence rate for flu (because winter quater consists of all 10 weeks) = 19/120 = 0.16%
e) if the 5 students dropped the class for a reason other than flu then our incidence rate in part a) will change to 14/120 = 0.12%
f) Prevalence of flu at the beginning of the quarter will be 0 because no students were afftected with flu when the winter quarter started.