Kelly Chase
811-54-6093
PH 601
Lindsey
9/14/09
Homework #1
Given:
Ate Egg Salad
Did Not Eat Egg Salad
Number of People who Ate Specific Food
Ate Tuna
75
200
Did Not Eat Tuna
100
50
Number of People who Ate Specific Food and Later Got Sick
Ate Tuna
Did Not Eat Tuna
Ate Egg Salad
60
75
Did Not Eat Egg Salad
70
15
New Table:
Egg Salad
Tuna
Both
Ate
Fell Ill
AR
175
275
75
135
130
60
.77
.47
.80
Did Not
Eat
250
150
15
Fell Ill
AR
RR
85
90
15
.34
.60
1.0
2.3
.78
.80
2.2) What is the sore throat attack rate in persons who ate both egg salad and tuna?
This corresponds to the AR column in the ‘both’ row. This is italicized above.
AR(both) = 60/75 = .80 = option (a)
2.3) Which of the following food items (or combination) is most likely to be infective?
The egg salad is most likely to be infective since it has a risk ratio of 2.3, the only risk ratio larger than 1
amongst the items. This corresponds to option (b).
3.2) A prevalence study conducted from January 1 through December 31, 2003, identified 1,000 cases of
schizophrenia in a city of 2 million persons. The incidence rate of schizophrenia in this population is
5/100,000 persons each year. What percent of the 1,000 cases were newly diagnosed in 2003?
# of new cases = IR x population =
Percent of newly diagnosed cases
5
𝑥 2,000,000 = 100
100,000
# 𝑜𝑓 𝑛𝑒𝑤 𝑐𝑎𝑠𝑒𝑠
100
= # 𝑜𝑓 𝑐𝑎𝑠𝑒𝑠 (𝑝𝑟𝑒𝑣𝑎𝑙𝑒𝑛𝑐𝑒) = 1,000
= 𝟏𝟎%
3.6) What is the incidence rate of active TB cases in a 6-month period?
Given:
Population = 183,000
# of new cases of TB occurring between 1/1 and 6/30/2003 = 26
# of active cases of TB on 6/30/2003 = 264
# 𝑜𝑓 𝑛𝑒𝑤 𝑐𝑎𝑠𝑒𝑠
26
14
IR = # 𝑜𝑓 𝑝𝑒𝑜𝑝𝑙𝑒 (𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛) = 183,000 = .00014 = 100,000 (b)
3.7) What is the prevalence rate of active TB as of June 30th, 2003?
# 𝑜𝑓 𝑎𝑐𝑡𝑖𝑣𝑒 𝑐𝑎𝑠𝑒𝑠
264
144
Prevalence = # 𝑜𝑓 𝑝𝑒𝑜𝑝𝑙𝑒 (𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛) = 183,000 = .00144 = 100,000 (c)