Practice Exam Questions

Question 1

An Outbreak of disease refers to?

a) The presence of a new disease in a specified area
b) A disease with R0 > 0
c) A occurrence of a disease in excess of what is usually expected
d) A frequently occurring disease with large economical impact

Answer 1

c) A occurrence of a disease in excess of what is usually expected

Question 2

How are prevalence and incidence related?

a) Incidence = Prevalence x Duration of Disease
b) Prevalence = Incidence x Duration of Disease
c) Incidence and Prevalence are not related
d) Incidence = Prevalence x Animals at Risk

Answer 2

b) Prevalence = Incidence x Duration of Disease

Question 3

The term Incidence is used correctly when referring to;

a) Risk or probability of a disease
b) Rapidity of disease occurrence
c) All new cases of a disease over a period of time
d) All of the above

Answer 3

d) All of the above

Question 4

What is the difference between a ratio and a proportion?

a) The numerator is a subset of the denominator in a proportion but not in a ratio
b) The denominator includes the un-infected animals in a proportion but not in a ratio
c) The numerator is not a subset of the denominator in a proportion but is in a ratio
d) A ratio can be expressed as a percentage whereas a proportion can not.

Answer 4

a) The numerator is a subset of the denominator in a proportion but not in a ratio

Question 5

Describe a situation in which you might want to report a disease using a count. Why is using a count not usually sufficient?

Answer 5

A count may be used in a situation where there is not enough data to calculate incidence, prevalence, attack rate (or other disease measures) etc. This may occur during a Foot and Mouth outbreak where there are five animals affected and no further data is available (like size of the herd or when they became infected).
A count is not usually used as you need to determine it relative to population size and over what time period the information was collected or the individuals infected.

Question 6

What does the target population refer to?

a) The population that is sampled from
b) The population to which results from the study are to be generalised
c) The population (consisting of individual animals) that has been selected, through sampling, to be studied
d) The results of random sampling

Answer 6

b) The population to which results from the study are to be generalised

Question 7

Which of the following is NOT a non-probability sampling technique?

a) Judgement
b) Convenience
c) Cluster
d) Purposive

Answer 7

c) Cluster

Question 8

During a study on antimicrobial resistance, veterinarians were asked to send in any swabs that they took from infected wounds. This is a ?

a) Convenience sampling technique
b) Simple Random sampling technique
c) Systematic sampling technique
d) Cluster sampling technique

Answer 8

a) Convenience sampling technique

Question 9

Which of the following is NOT required to calculate the sample size required to identify whether disease is PRESENT or ABSENT in a herd?

a) The confidence required of the conclusion
b) The prevalence that the disease is likely to be present as if it is indeed present
c) The number of animals that have had the disease in the herd previously
d) The size of the population (herd) in question

Answer 9

c) The number of animals that have had the disease in the herd previously

Question 10

You want to estimate the prevalence of disease in a herd of cattle. You have no idea what the prevalence is likely to be in this herd as published estimates in a similar region range between 10% and 80%. What estimate of prevalence do you use for the sample size calculation?

a) 80%
b) 50%
c) 70% (80%-10%)
d) You do not need an estimate of prevalence for this sample size calculation

Answer 10

b) 50%

Question 11

Which of the following is correct?

a) Confidence = 1 - Beta
b) alpha = 1 - Beta
c) Confidence = 1 - alpha
d) Power = 1 - alpha

Answer 11

c) Confidence = 1 - alpha

Question 12

In which of the following situations is incidence smaller than prevalence?

a) Never
b) Diseases with a short duration
c) Chronic diseases
d) Diseases that do not result in immunity

Answer 12

c) Chronic diseases

Question 13

An advantage of a Stratified random sample is that:

a) It improves the precision of the estimate
b) It has a fixed sample size in each strata
c) All units in each strata are tested
d) All of the above

Answer 13

a) It improves the precision of the estimate

Question 14

Which measure of association is appropriate for use with case-control studies?

a) Relative Risk
b) Risk Ratio
c) Odds Ratio
d) Relative Risk or Risk Ratio

Answer 14

c) Odds Ratio

Question 15

Which of the following comments is wrong about cluster sampling:

a) It is often used and practical for field research
b) The estimate is precise
c) It is easy to select
d) All individuals within the cluster are usually tested

Answer 15

b) The estimate is precise

Question 16

Briefly discuss the relationship between prevalence of disease in a population and predictive values (positive or negative)

Answer 16

Positive predictive values increase with the prevalence of disease in a population and negative predictive values increase the lower the prevalence of disease in a population.

Question 17

How could you increase the positive predictive value of test results?

a) Test in a subset of the population that is more likely to have the disease
b) Use a highly specific test
c) Use multiple tests in a series
d) All of the above

Answer 17

d) All of the above

Question 18

What does Attributable Risk refer to?

a) It is a measure of the additional risk present when exposed to the risk factor
b) The incidence of disease in the exposed group minus the incidence of disease in the unexposed group
c) The difference in disease frequency between the group exposed to a certain risk factor and the group that is not exposed to that risk factor
d) All of the above

Answer 18

d) All of the above

Question 19

Where do clinical trials fall in the ‘hierarchy of evidence’ pyramid?

a) Towards the top (these studies result in very good evidence)
b) Towards the bottom (these studies result in not so good evidence)
c) At the very top of the pyramid (these studies result in the best evidence possible)
d) There is no such thing as the ‘hierarchy of evidence’ pyramid

Answer 19

a) Towards the top (these studies result in very good evidence)

Question 20

Briefly describe the difference between confounding and interaction.

Answer 20

Interaction-

Confounding-

Question 21

What does the term ‘blinding’ mean with respect to clinical trials?

a) That all researchers wear blindfolds while conducting the experiments
b) That the researcher or recipient is not aware of the treatment being given
c) That the researcher knows no more than the recipient about the study
d) That the trial has been set up by someone who does not understand the research question

Answer 21

b) That the researcher or recipient is not aware of the treatment being given

Question 22

What is an ‘attack rate’?

a) Number of new cases / population at risk
b) Number of new cases / entire population
c) Number of cases at T1 / number of cases at T0
d) Number of overall cases / time frame of outbreak

Answer 22

a) Number of new cases / population at risk

Question 23

Which of the following studies would you be most likely to carry out to refine your hypotheses in an outbreak investigation that required prompt identification of a causative agent?

a) Cohort study
b) Case-control study
c) Randomised controlled trial
d) Meta-analysis

Answer 23

b) Case-control study