Essential Epidemiology An Introduction For Students and Health Professionals 3rd Webb Test Bank
Essential Epidemiology An Introduction For Students and Health Professionals 3rd Webb Test Bank
Essential Epidemiology An Introduction For Students and Health Professionals 3rd Webb Test Bank
4. What is the difference between the incidence proportion and the incidence rate?
A. The incidence proportion measures the proportion of people who develop disease
during a specified period, whereas the incidence rate measures how quickly people
are developing disease
B. The incidence proportion measures how quickly people are developing disease,
whereas the incidence rate measures the proportion of people who develop disease
during a specified period
C. The incidence proportion measures the number of people with disease in a
population at a specific point in time, whereas the incidence rate measures the
number of new cases of disease that occur in the population.
D. None of the above
Answer: A. The incidence proportion measures the proportion of people who develop
disease during a specified period. It presents the number of new cases in a designated
time period (the numerator) as a proportion of the total number of people at risk at the
start of the period (the denominator) and has no units e.g. 1% (in six months). In
contrast, the incidence rate measures how quickly people are developing disease over
time and it has units of time e.g. 10 per 1000 per year.
5. A new treatment is developed that prevents death but does not produce recovery
from a previously lethal disease. Which of the following will occur?
Answer: A. Prevalence is a function of incidence (the rate at which new cases of disease
occur) and duration (how long an incident case continues to have the disease). If cases
no longer die from the disease their duration of life with the disease present necessarily
increases, hence prevalence increases. The new treatment will not, however, affect how
quickly new cases occur so it will not affect the incidence of the disease.
6. A study aims to determine the incidence and prevalence of a particular disease within
the local government area of Winchelsea. What factors would decrease the
prevalence of the disease within this study catchment area?
denominator without a change in the numerator (C) necessarily reduces the size of the
measure.
7. The following table shows data from an epidemiological study. What is the incidence
rate among those who are exposed to the factor under study?
Answer: A. The incidence rate in the exposed = 700 ÷ 1950 py = 0.359 = 35.9 per 100 py.
It would be 359 per 1000 py (C) or 35,900 per 100,000 py (B).
8. According to the table below, which food is the most likely cause of the outbreak of
food poisoning?
Food Number of people Number who ate
who ate that food the food and got
sick
Cold chicken 86 34
Potato salad 54 38
Egg sandwiches 76 40
Fruit pie and cream 32 12
Cheese 48 12
A. Cold chicken
B. Potato salad
C. Egg sandwiches
D. Fruit pie and cream
E. Cheese
Answer: B. The potato salad is the most likely culprit because it has the highest attack
rate (38 ÷ 54 = 70.4%). This can’t be definitive, given the challenges of recall and the fact
that most people will eat a number of foods in addition to that causing the problem, but
it (and to a lesser extent the egg sandwiches, attack rate = 40 ÷ 76 = 52.6%) stand out
from the crowd, and both are known to be potential sources of food poisoning.
Food Number of people Number who Attack
who ate that food ate the food Rate
and got sick