Sample EPI questions with answers and explanation.
1. A study is conducted for a pharmaceutical agent that has shown promise for reducing heart disease among women. In order to more fully test the agent, an additional study is done restricting the participants to be randomized to those who have a history of hypertension. Which of the following advantages cannot be claimed by the researchers?
a) Power of the study is increased
b) Potential benefits in high-risk populations are increased
c) Validity of the study is increased by focus on a Professional assignment writing help “Sample EPI nursing practice exam and explanation” Meet the team that makes it all possible homogenous population
d) The generalizability of the study is increased
e) The overall cost of the study is decreased
Answer. D) The generalizability of the study is increased
Explanation. Explanation: Restricting the study to a high-risk group will only fail to increase the generalizability of the findings since the study results will apply only to a more specific group of women who share a history of hypertension.
2. A randomized, double-blind Professional assignment writing help “Sample EPI nursing practice exam and explanation” Meet the team that makes it all possible clinical trial of a varicella vaccine observed an estimated incidence of 25% chickenpox episodes in persons receiving the vaccine, compared to 80% among persons receiving a placebo. The estimated efficacy of the vaccine is:
Answer. C) 68.8%
Explanation: The efficacy is calculated by subtracting the rate in those vaccinated from the placebo rate and dividing by the placebo rate. In this example, 80% minus 25% equals 55%. Dividing by 80% results in an efficacy of 68.8%.
3. A multicenter double-blind randomized study was carried out to compare the effect of drug X with that of a placebo in patients surviving acute myocardial infarction (AMI). Treatment with the drug started 7 days after infarction in 1,884 patients, 52% of all persons who were evaluated for entry into the study. 945 participants were randomized to treatment with drug X while 939 were assigned to the placebo group. Patients were then followed for 12 months for reinfarction. There were 152 deaths in the placebo group and 98 in the group receiving drug X.
After entry into the study, patients were first classified into three groups, those who had a previous AMI, those with a first AMI who were at high risk for other cardiovascular diseases such as congestive heart failure, and those with a first AMI who were at low risk for other cardiovascular diseases. Which term best describes the study design?
a) Cohort study
b) Randomized clinical trial with crossover design
c) Randomized clinical trial with factorial design
d) Randomized clinical trial with stratified randomization
e) Case study design
Answer. D) Randomized clinical trial with stratified randomization
Explanation: The study design is a multicenter randomized clinical trial with a stratified design. The participants are classified into one of three strata, then randomized to either drug X or placebo groups. They are then followed for 1 year after entry into the study.
4. A study is planned to investigate the relationship of factors associated with maternal hypertension and the risk of congenital birth defects in children born to these women. Which of the following would be a reason for using a cohort study design?
a) The need to obtain data on the incidence Professional assignment writing help “Sample EPI nursing practice exam and explanation” Meet the team that makes it all possible of early fetal losses due to congenital birth defects
b) The low rate of congenital birth defects
c) The development of pregnancy-related hypertension in asymptomatic women
d) The consistency of recall of risk factors among women having children with and without congenital birth defects and those having children
e) Testing hypotheses about several different risk factors for congenital birth defects such as maternal age, diabetes, and previous miscarriage history
Answer. A) The need to obtain data on the incidence of early fetal losses due to congenital birth defects
Explanation: The cohort design is best for observing the incidence of a disease in persons who do not have the outcome at baseline. In this study, the researchers will start with women planning on becoming pregnant and stratify them by presence of hypertension. Since all women will be followed over time, the occurrence of fetal loss can be tracked by the investigators during the study.
5. A researcher is interested in the etiology of myocardial infarction (MI) among men between 18 and 40 years of age. Her hypothesis concerns the influence of diets high in fat and subsequent development of MI. What is the best study approach to address this hypothesis?
a) Case-control study with cases of MI identified post-event and controls sampled from healthy men in the population, then have both groups complete dietary surveys
b) Case-report study describing the dietary habits in 100 men having an MI
c) Ecologic study with the rates of MI compared between cities with higher-than-average dietary fat intakes and cities with lower-than-average dietary fat intakes
d) Retrospective cohort study with medical records used to collect information on diet among men with and without an MI
e) Prospective cohort study identifying a population of men in this age group, administering a dietary survey and classifying men by high and low-fat diet, then following both groups for the development of an MI Professional assignment writing help “Sample EPI nursing practice exam and explanation” Meet the team that makes it all possible
Answer. E) Prospective cohort study identifying a population of men in this age group, administering a dietary survey and classifying men by high and low-fat diet, then following both groups for the development of an MI
Explanation: The choice of a prospective cohort study allows the researcher to select the population of interest (men ages 18 to 40 years), classify the exposure after an initial assessment, and then follow all men in the study for incident outcomes. This approach is best described as a cohort study.
6. Which of the following is an advantage to the conduct of a cohort study?
a) The study population is the same with regard to the risk factors for disease
b) The disease under study occurs rarely in the population
c) The incidence of the disease is high in the nonexposed group
d) The incidence of the disease is high in the exposed group
e) The study population includes a high number of undiagnosed, asymptomatic individuals with the disease
Answer. D) The incidence of the disease is high in the exposed group
Explanation: A cohort study entails classification of the study population by exposure to the risk factor of interest. The subsequent incidence of disease occurs during the follow-up time of observation of the study population. A high incidence of disease in the exposed group provides the researcher with a large number of outcomes and provides an initial association with the risk factor if the disease occurs in the exposed group.
7. A cohort study is planned to investigate the potential adverse health effects of daily alcohol consumption. In assessing the risk of liver cancer related to alcoholism, which of the following is not an important methodologic consideration?
a) The need to study a large number of persons for a rare disease outcome
b) The difficulty of finding enough Professional assignment writing help “Sample EPI nursing practice exam and explanation” Meet the team that makes it all possible persons with liver cancer at the beginning of the study in whom alcohol consumption could be determined
c) The possible bias associated with persons describing alcohol usage
d) The likelihood that doctors would monitor alcoholics more closely for liver cancers
e) The possibility that persons would change their alcohol consumption practices during the study period
Answer. B) The difficulty of finding enough persons with liver cancer at the beginning of the study in whom alcohol consumption could be determined
Explanation: A cohort study must take into account methodologic issues related to rare disease occurrences, classification of exposure throughout the study conduct, and potential biases related to identifying outcome events. Ideally, a cohort study would start with no diseased individuals who are followed over time, thus finding persons with liver cancer at the beginning of the study would not be a consideration for a cohort study design.
8. Which of the following is not an advantage of a retrospective cohort study?
a) Allows for the study of many disease outcomes resulting from an exposure
b) Incidence rates can be calculated
c) Possible bias due to selection of the cohort is eliminated
d) Potential recall bias can be minimized
e) Requires less follow-up time than a prospective cohort study
Answer. C) Possible bias due to selection of the cohort is eliminated
Explanation: Retrospective cohort studies depend on the ability of researchers to identify eligible cohort members, describe their past exposure using historical records, and to follow the cohort until the disease develops. Relying on past records to select persons for entry into the cohort study could be compromised by biases regarding the investigator’s theorized association of the exposure and disease.
9. Which of the following may be a factor that would result from the inability to use randomization in a cohort study?
a) The possibility that a factor which leads to exposure may be causally associated with the disease
b) The possibility that a higher proportion of exposed persons may be included in the study
c) The possibility that a higher proportion of non exposed persons may be included in the study
d) The study will take longer to conduct if randomization is not used
e) The possibility that several different types of diseases will develop in the study population
Answer. A) The possibility that a factor which leads to exposure may be causally associated with the disease
Explanation: Randomization removes potential bias from the designation of treatment, or exposure, groups. Without this step, it may be likely that the exposed and nonexposed groups in a cohort study are misidentified due to other factors that are associated with exposure and subsequent disease outcomes.
10. In 2002, investigators started a study of the association of cholesterol levels and stroke in a group of 2,000 healthy persons who had participated in a cholesterol screening program in 1992. Professional assignment writing help “Sample EPI nursing practice exam and explanation” Meet the team that makes it all possible The investigators determined exposure categories using cholesterol levels in all persons that were measured at the time of the screening program. A cutoff value of 200 mg/dL was used to define “high” cholesterol while those with levels below 200 were identified as having “low” cholesterol. Using this definition, 1,000 persons had “high” cholesterol levels while the remaining 1,000 persons had “low” cholesterol. The investigators determined that 150 cases of stroke occurred by the end of 2004, with 113 cases occurring in the high cholesterol group. What is the study design that the investigators used?
a) Case-control study
b) Retrospective cohort study
c) Prospective cohort study
d) Cross-sectional study
e) Randomized clinical trial
Answer. B) Retrospective cohort study
Explanation: In this study, a study population is determined to include persons who were disease-free at baseline. Using historical records, exposure status was determined for the study population. Subsequent observation enabled the researchers to ascertain incident cases of stroke among those included.
11. The effect of exposure to high-density automobile traffic either as a bicyclist or pedestrian was compared to minimal or no exposure to automobile traffic. It is hypothesized that direct exposure to automobile traffic has an effect on acute myocardial infarction (MI). This association was studied with 500 incident cases of MI diagnosed in the emergency rooms of several hospitals and compared to 1,000 other subjects who visited the same emergency rooms for reasons other than cardiovascular and respiratory diseases. All subjects were asked to report the amount of time that they spent exposed to high-density traffic over the past month prior to their hospital visit.
What type of study design is this?
c) Retrospective cohort Professional assignment writing help “Sample EPI nursing practice exam and explanation” Meet the team that makes it all possible
d) Prospective cohort
e) Randomized clinical trial
Answer. B) Case-control
Explanation: The study design relies on hospital-based recruitment of cases (persons with an MI) and controls (other patients in the emergency room who did not have cardiovascular and respiratory diseases which may be associated with air pollution). The exposure under investigation is a time-dependent measure of exposure to high-density automobile traffic in the days preceding the emergency room visit.
12. Which of the following is an advantage of the case-control study design?
a) Recall bias is avoided
b) Little to no bias when assessing the outcome of interest
c) It is possible to study more than one exposure
d) It is possible to study more than one disease outcome
e) The study design is useful for studying rare exposures
Answer. C) It is possible to study more than one exposure
Explanation: Case-control studies start with a definition of those with a specific disease outcome, cases, and compare these persons to those without the outcome of interest, controls. A wide range of exposures can be included for assessment in the study groups and can be evaluated using the preferred measure of association, the odds ratio.
13. Which of the following statements about person-years is not true?
a) It allows for different lengths of follow-up time among study subjects
b) It is a valid denominator for estimates of risk for individuals
c) 20 persons followed for 5 years each contribute the same amount of person-years as 200 subjects followed for 6 months each
d) It is the amount of time that a subject was without the outcome
e) Person-years are not calculated for time during a study when outcome status is not known for subjects lost to follow-up
Answer. B) It is a valid denominator for estimates of risk for individuals
Explanation: Person-years are a useful way to measure the rate at which events occur in a group of persons followed for different periods. However, the risk in any person-year may not be the same for different individuals. This may be true when evaluating persons for a disease with a long latency period such as cancer. A study that includes 5,000 persons for 2 years may not have an equivalent underlying risk as a study of 1,000 persons followed for 10 years.
14. Investigators wanted to know if some military personnel are more error prone than others and would be a poor risk for training as a pilot. A study was done in which individuals who had injuries during basic training were compared to individuals who had not had an injury during training. Both groups were asked to recall episodes during childhood when they had had accidents that resulted in an injury. The individuals with a training injury reported more incidents during childhood when they had an injury. Therefore, the military command concluded that some persons are more likely to be error prone and that individuals with a childhood injury should be excluded from pilot training.
One commanding officer disagreed with this conclusion. He asked the investigators to design a second study in which all individuals were asked about childhood injuries prior to the start of basic training. The group who reported having a childhood injury was compared to the group who had not had a childhood injury to determine which group had a higher rate of injuries during basic training. At the end of follow-up, there was no difference in the rate of injuries experienced by each group.
What type of study design was used for the second study?
c) Retrospective cohort
d) Prospective cohort
e) Randomized clinical trial
Answer. D) Prospective cohort
Explanation: The second study was Professional assignment writing help “Sample EPI nursing practice exam and explanation” Meet the team that makes it all possible prospective and had two groups: those who reported childhood injury (“exposed”) compared to those who did not have a childhood injury (“non exposed”). Outcome status was assessed after follow-up through basic training though no information is given that investigators were blinded to exposure status when determining whether or not a training-related injury occurred.