Question: Residents of three villages with three different sources of water were asked to participate in a one-time survey to identify the prevalence of cholera carriers. Because several cholera deaths had occurred recently, virtually everyone present at the time completed the survey. The proportion of residents in each village who were carriers was computed.
What is the classification of this study?
Answer Options:
A. Cross-sectional study
B. Case-control study
C. Prospective cohort study
D. Retrospective cohort study
E. Experimental study
Answer: A. Cross-sectional study
Question: What type(s) of bias is/are most problematic in a case-control study? (Select all that apply.)
Answer Options:
A. Attrition
B. Selection bias
C. Recall bias
D. Measurement bias
Correct Answers:
B. Selection bias
C. Recall bias
Question 13
Below are listed advantages of case-control and prospective cohort studies.
Fill in the blank with either:
a. Case-control
b. Prospective cohort
Studying rare exposures
Studying rare outcomes
Less prone to recall biases
Less risk of selection bias
Typically quicker and less expensive to conduct
Usually requires fewer subjects
Correct Answers:
b (Prospective cohort)
a (Case-control)
b (Prospective cohort)
b (Prospective cohort)
a (Case-control)
a (Case-control)
Compute the odds ratio for the risk of cardiac death if the “Gender” variable is female, after adjusting for all other variables. Note: Female = 1.
Answer Options:
A. 0.278
B. 0
C. 1.32
D. 1
Answer: C. 1.32
Question: To investigate the relationship between dietary aflatoxins and hepatocellular carcinoma (HCC), cases of liver cancer were identified and matched to liver cancer-free controls using data from a cohort study. The exposure of interest, aflatoxins, was assessed in both the subjects with cancer and controls without cancer using a questionnaire collected at the beginning of the study.
What type of study was conducted?
Answer Options:
A. Cross-sectional
B. Retrospective cohort
C. Case-Control
D. Experimental Trial
Answer: C. Case-Control
Question: Investigators aimed to estimate the prevalence of high ibuprofen consumption (more than 21 units per week) among adult residents of a large city. A random sample of adults registered with local general practitioners was selected, and a questionnaire about NSAID usage was sent. This design excluded city residents not registered with a doctor, potentially missing individuals with different patterns of ibuprofen use.
What is the result of not including the residents without a doctor?
Answer Options:
A. Testing bias
B. Selection Bias
C. History bias
D. Attrition bias
Answer: B. Selection Bias
Question: Retrospective cohort studies are characterized by all of the following EXCEPT:
Answer Options:
A. The groups are exposed and unexposed
B. Incidence rates may be calculated
C. The required sample size is smaller than needed for a prospective cohort study
D. The required sample size is similar to that needed for a prospective cohort study
Answer: D. The required sample size is similar to that needed for a prospective cohort study
Question: Which of the following are assumptions of linear regression? (Select all that apply.)
Answer Options:
A. The errors have a constant variance represented as σ²
B. The observations are independent
C. The relationship between X and Y can have any distribution
D. The observations constitute a random sample from the population of interest
Correct Answers:
A. The errors have a constant variance represented as σ²
B. The observations are independent
D. The observations constitute a random sample from the population of interest
Question 24
Troponin levels are known to be associated with MI; however, researchers are interested in determining what covariates may predict troponin levels using a linear regression.
Which of the following is an appropriate outcome measure in your regression analysis?
Answer Options:
A. Troponin levels in the study population
B. CRP levels
C. CK-MB levels
D. Prior occurrence of an MI
Answer: A. Troponin levels in the study population
Question: Match the LETTER of the observational study design below to each scenario.
An investigator wishes to determine if the prevalence of RSV is higher among infant boys than infant girls
Health officials in Baltimore believe that a smoking cessation program in combination with cessation medications will be more effective than the program alone
Investigators wish to determine the development of potential health outcomes from heavy drinking among young adults
A researcher describes a detailed examination of a real-world patient who had an adverse reaction to a medication
Study Designs:
a. cross-sectional
b. case-control
c. prospective cohort
d. case report
Correct Answers:
a. cross-sectional
c. prospective cohort
c. prospective cohort
d. case report
Question 8
Clinician researchers long believed that hyperacidity was the only risk factor associated with peptic ulcer disease (PUD). However, in 1982 they discovered H. pylori in the stomachs of patients with PUD and designed a study to determine if there was a relationship between H. pylori and PUD. The researchers identified patients who had PUD and matched them to individuals who did not have PUD. They determined the odds of being exposed to H. pylori in the presence of PUD compared to the odds of being exposed to H. pylori without PUD.
What type of study is this?
Answer Options:
A. Retrospective cohort
B. Cross-sectional
C. Case report
D. Case-control
Answer: D. Case-control
Question: Researchers are interested in studying covariates that are associated with, or are predictors of, troponin levels using linear regression.
Which of the following may be included as independent variables in a linear regression model? (Select all that apply.)
Answer Options:
A. Total cholesterol (mg/dL)
B. Family history of MI
C. LDL-c categories: High, normal, low
D. Methylenetetrahydrofolate reductase gene
Correct Answers:
A. Total cholesterol (mg/dL)
B. Family history of MI
C. LDL-c categories: High, normal, low
D. Methylenetetrahydrofolate reductase gene
Question 26
Which of the following is true about a confounding variable? (Select all that apply.)
Answer Options:
A. It is a variable that is associated with the outcome of interest and with the exposure (aka risk factor) that modifies/distorts the relationship between the exposure and the outcome.
B. A confounder can be “adjusted for” in a regression analysis
C. It is a third variable that differs at differing levels of the risk factor
D. It is only important in a linear regression analysis
Correct Answers:
A. It is a variable that is associated with the outcome of interest and with the exposure (aka risk factor) that modifies/distorts the relationship between the exposure and the outcome.
B. A confounder can be “adjusted for” in a regression analysis
C. It is a third variable that differs at differing levels of the risk factor
#1.
Question: A special procedure that a nursing assistant might perform is
Answer Options:
A. giving medications
B. starting an IV
C. preparing a Sitz bath
D. preparing a gavage feeding
Answer: D. preparing a gavage feeding
Question: Records of the physical examination of the entire incoming freshman class of 1975 at the University of Minnesota were examined in 2005 to determine if their recorded demographics at the time of admission to the university were related to the development of CHD by 2005.
What is the classification of this study?
Answer Options:
A. Cross-sectional study
B. Case-control study
C. Prospective cohort study
D. Retrospective cohort study
E. Experimental study
Answer: D. Retrospective cohort study
Question: In cohort studies of the role of an exposure in the development of disease, it is essential that:
Answer Options:
A. There be equal numbers of persons in both study groups
B. At the beginning of the study, individuals with the disease and without the disease have equal risks of having the exposure
C. The exposed and the unexposed groups be as similar as possible except with regards to the exposure
D. Cases with the disease at the beginning of the study are identified similarly to the controls
Answer: C. The exposed and the unexposed groups be as similar as possible except with regards to the exposure
Question: To investigate the relationship between dietary aflatoxins and hepatocellular carcinoma (HCC), all patients who were identified with liver cancer were matched to liver cancer-free controls using data from a pre-existing cohort study. The exposure of interest, aflatoxins, was assessed in both the subjects with cancer and controls without cancer with questionnaires collected at the beginning of the study.
What is the only measure of association that is appropriate to calculate for this type of study?
Answer Options:
A. Relative Risk
B. Beta Coefficient
C. Odds Ratio
D. Absolute Risk
Answer: C. Odds Ratio
Question: Which of the following analyses can adjust for multiple independent variables that are categorical? (Select all that apply.)
Answer Options:
A. Linear Regression
B. Logistic Regression
C. t-test
D. Odds ratio from a 2×2 table
Correct Answers:
A. Linear Regression
B. Logistic Regression
Question 22
You wish to conduct a study to determine if Ozempic is effective if the dosing regimen is every 2 weeks. You think of several diabetic outcomes, yet you wish to use a linear regression analysis.
Which of the following would be an appropriate scale of data for the outcome measure in your study?
Answer Options:
A. Foot inspection discovered an incident diabetic foot infection
B. A1C below 6.5
C. Serum glucose, fasting level below 90 (yes/no)
D. Time in appropriate blood glucose range (in minutes)
Answer: D. Time in appropriate blood glucose range (in minutes)
Question: In the course of conducting a study, subjects’ blood pressure was measured 3 times in a row. The blood pressures were never exactly the same—sometimes a little high, and sometimes a little low.
What type of error is this?
Answer Options:
A. Systematic error (bias)
B. Random Error (random variation)
C. Confounding/misclassification error
D. Selection error
Answer: B. Random Error (random variation)