Question

Need C and D the most others are mainly for reference

4. An outbreak of gastroenteritis occurred at a liberal arts college with a student enrollment of 1164. Forty-seven (47) students had sought care at the college Health Center between 10:30 p.m. on January 17 and 8:00 p.m. on January 18. The ill students seen at the Health Center all lived in dormitories totaled 756. The dormitory of residence of the 47 known cases, as well as the population and gender of the occupants of each dormitory is shown in the table below:

Dormitory         Gender           Pop.    Of    Dormitory          Number of Cases______

1 F 80 19

2 F 62 2

3 F 89 0

4 F 61 1

5 F 53 5

6 F 35 0

7 F 63 0

8 F 103 4

9 M 35 1

10 M 37 0

11 M 34 1

12 M 62 13

13 M 32 1

14 M 10 0         

_________________________________________________________________

Use the above information to answer the following:

(a) Calculate the combined attack rate of the two most affected dormitories.

(b) Calculate the attack rate for the remaining 12 dormitories.

(c) Compare the attack rates calculated in “a” and “b” above. Explain this ratio.

(d) What proportion of the cases were in the two most affected dormitories? Total number cases in two over total number affected

(e) Calculate and compare the sex-specific rates for the dormitories population.

Answer 1

a) Attack rate = no of new cases in the specified time period/total population at the start.

two most affected dorms = 1 and 12.

Combined attack rate = cases from the dorms = 19+13 = 32

Ttoal population of the dorms = 142

Attack rate = 32/142 = 0.2253

b) Attack rate for remaining 12 dorms = cases = 15

Total population of remaining 12 dorms = 614.

Attack rate = 0.0244

c) The attack rates in case (a) are 0.225 whereas in the other 12 dorms combined, it is 0.024. The attack rate of the two most affected dorms is almost 10 fold more than the attack rate in the rest of the 12 dorms.

d) The proportion of cases in the two most affected dorms = no of cases in the 2 dorms/total no of cases = 32/47 =0.6808.

e) Total no of females affected = 31

Ttoal female population in the dorms = 546.

Attack rate in females = 31/546 = 0.056

Total no of males affected = 16

Ttal male population in the dorms = 210

Attack rate in males = 0.076

The attack rate in males is 0.73 times higher than that in females.