BISTATS 20 QUESTION MULTIPLE CHOICE HOMEWORK TO BE DONE IN 3 HOURS

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QUESTION 1

1. Which of the following are potential limitations of validity studies?

	a.	The ‘gold standard’ used may not itself be entirely valid.
	b.	Selection bias can result in the non-generalizability of the validity levels estimated.
	c.	Validity studies often involve small samples and thus their estimates are imprecise.
	d.	All of the above.

QUESTION 2

1. A hypothetical cohort study tested the association between intimate partner violence (IPV) and the occurrence of mood disorders in middle-aged women. Women who had been victims of IPV were 3.2 times more likely to be diagnosed with mood disorders than women who had not experienced IPV. After adjusting for several possible confounders, the odds ratio was adjusted to 2.5. Using an additive scale, how much of the excess risk was explained by the confounding variables?

	a.	31.8%
	b.	21.9%
	c.	28.0%
	d.	78.1%

QUESTION 3

1. There is a city (City Q) that has an age-adjusted mortality rate of 125 deaths per 100,000 persons per year. This was calculated by the direct standardization method using the non-institutionalized population of the United States as the standard population. What is the best interpretation of this mortality rate?

	a.	City Q would have had a mortality rate of 125 deaths per 100,000 people per year if it had the same age distribution as did the non-institutionalized population of the United States.
	b.	The difference in mortality rates between the United States and City Q is not due to age.
	c.	City Q has the same age distribution as the non-institutionalized population of the United States
	d.	City Q had 125 deaths per 100,000 people last year.

QUESTION 4

1. Which of the following is not a situation that can produce selection bias in a case-control study? Choose the best answer.

	a.	The disease status has some influence on the recall of exposures.
	b.	The exposure has some influence on the process by which controls are selected.
	c.	The exposure has some influence on the process of case ascertainment.
	d.	All of the above will produce selection bias.

QUESTION 5

1. In a large case control study of the relationship between knee pain and physical activity, the crude odds ratio for knee pain in those who participated in no physical activity vs. weekly physical activity was 4.5. When the association between knee pain and physical activity was stratified by body mass index (BMI), the odds ratios for knee pain were 7.0 for persons who were severely obese, 4.5 for those who were overweight, and 2.0 for those of normal weight. The Mantel-Haenszel BMI-adjusted odds-ratio was 4.0. The most appropriate summary of the results of this study would be:

	a.	the crude odds ratio of 4.5, because the Mantel-Haenszel summary odds ratio should not be used when there is substantial effect modification.
	b.	the three stratum-specific odds ratios of 7.0, 4.5 and 2.0, because there appears to be confounding.
	c.	the three stratum-specific odds ratios of 7.0, 4.5 and 2.0, because there appears to be effect modification.
	d.	the Mantel-Haenszel summary odds ratio of 4.0, because it adjusts for confounding by BMI and represents the magnitude of risk associated with lack of physical activity in each of the groups.

QUESTION 6

1. Consider a case-control study of the relationship between oral contraceptive use and diabetes diagnosis. Because oral contraceptive use is likely to be related to a higher average frequency of medical encounters, any subclinical disease is more likely to be diagnosed in oral contraceptive users than in nonusers. What type of bias is most likely to be present in this situation?

	a.	Medical surveillance bias
	b.	Respondent bias
	c.	Berksonian bias
	d.	Recall bias

QUESTION 7

1. Consider this hypothetical study: A researcher conducted a cross-sectional study to look at the association between drinking coffee and the occurrence of dental caries. She stratified the data by gender and obtained the following tables:

The stratified odds ratios for the association between coffee drinking and dental caries are:

OR (males) = 1.72; OR(females) = 0.43

OR (males) = 0.58; OR (females) = 2.33

OR (males) = 0.33; OR (females) = 3.03

OR (males) = 0.69; OR (females) = 1.67

QUESTION 8

1. During the conduct of a study, healthy subjects were more likely than sick subjects to refuse to allow subsequent follow-up contacts. What effect would this be likely to have on the calculation of cumulative incidence?

	a.	Underestimation
	b.	Overestimation
	c.	Variable (either over- or under-estimation)
	d.	No effect Consider this hypothetical study: A researcher conducted a case-control study to look at factors associated with suicide. The medical and employment records of 500 persons who died by suicide were compared to 500 records of citizens in the state. The following results from a logistic regression analysis were obtained:

QUESTION 9

1. Consider this hypothetical study: A researcher conducted a case-control study to look at factors associated with suicide. The medical and employment records of 500 persons who died by suicide were compared to 500 records of citizens in the state. The following results from a logistic regression analysis were obtained:

In the above models, which groups of factors were shown to be confounders of the depression-suicide association?

Group 1: Gender and age only

Group 2: Being in a committed relationship and employment status only

Groups 1 & 2: Gender and age, as well as being in a committed relationship and employment status, were confounders of the depression-suicide association

None of the factors were confounders of the depression-suicide association

QUESTION 10

1. Consider these hypothetical data: A prospective cohort study was conducted to examine the association between regular use of sunscreen (exposure) and developing melanoma (outcome); the researchers were also interested to see if age was an effect modifier of this association. Here are the study results:

The attributable risk of melanoma in younger sunscreen users compared to younger nonusers is:

	a.	AR =115
	b.	AR= 143
	c.	AR = 25
	d.	AR = 86
QUESTION 11 1. A hypothetical study was conducted with 20 participants to investigate the 2-year survival probability of persons diagnosed with liver cancer. Kaplan-Meier survival estimates resulted in the table below: 2.

What is the value that should be in the cell labeled (A)?

	a.	0.050
	b.	0.950
	c.	0.048
	d.	0.200

12) Observe the following directed acyclic graph (DAG):

In this model, how many causal pathways are shown between (X) and (Y)?

	a.	0
	b.	1
	c.	2
	d.	3

QUESTION 13

The effect of age was confounded by relationship and employment status.

True

False

QUESTION 14

1. A hypothetical study was conducted with 20 participants to investigate the 2-year survival probability of persons diagnosed with liver cancer. Kaplan-Meier survival estimates resulted in the table below:

What is the value that should be in the cell labeled (C)?

	a.	0.632
	b.	0.092
	c.	0.875
	d.	0.917

QUESTION 15

1. Under which conditions is loss-to-followup most likely to result in selection bias in a cohort study?

	a.	If the loss-to-followup is associated with the exposure only.
	b.	If the loss-to-followup is associated with both the exposure and the outcome.
	c.	If the loss-to-followup is associated with the outcome only.
	d.	If the loss-to-followup is associated with neither the exposure nor the outcome.

QUESTION 16

1. A study evaluating the effectiveness of a regular occult blood test screening for colorectal cancer found that the screening program is effective. Further analysis revealed that cases detected by the screening procedure had a better prognosis than cases diagnosed between screening exams. This is an example of:

Lead time bias

Misclassification bias

Length bias

Screening bias

QUESTION 17

1. In a study investigating the relationship between poor maternal mental health and preterm birth, poor maternal mental health and pregnancy complications are both shown to cause preterm birth. Poor maternal mental health is also shown to cause pregnancy complications. In this study, the best description of pregnancy complications is that they are:

	a.	An intermediate variable in the pathway between mental health and preterm birth.
	b.	A confounder of the mental health – preterm birth association.
	c.	An effect modifier of the mental health—preterm birth association.
	d.	Not a factor in the mental health –preterm birth association.

QUESTION 18

1. A study assessed the occurrence of past child abuse in college students through the use of a questionnaire. If the researchers wanted to determine the reliability of the assessment of child abuse by administering the questionnaire to the same participants one month apart and comparing the results, which of the following measures would they use (choose one)?

	a.	Sensitivity analysis
	b.	Interclass correlation coefficient
	c.	Standard error
	d.	Kappa statistic

QUESTION 19

1. A hypothetical case-control study found that regular coffee drinkers were 1.8 times more likely to report a positive sense of well-being than non-coffee drinkers (OR = 1.8; 95% CI = 1.3-2.4). When the results were stratified by gender, the odds ratio for women was 1.1 (95% CI = 0.9-1.3) and the odds ratio for men was 0.9 (95% CI = 0.7-1.1). Which of the following statements best describes the role of gender in the association of coffee drinking and sense of well-being?

	a.	Gender is both a confounder and an effect modifier of the association between coffee drinking and sense of well-being.
	b.	Gender is a confounder of the association between coffee drinking and sense of well-being.
	c.	Gender is an effect modifier of the association between coffee drinking and sense of well-being.
	d.	Gender is neither a confounder nor an effect modifier of the association between coffee drinking and sense of well-being.

QUESTION 20

Which of the following statements best describes the role of gender in the association of coffee drinking and dental caries?

	a.	Gender is an effect modifier of the association between coffee drinking and dental caries.
	b.	Gender is both a confounder and an effect modifier of the association between coffee drinking and dental caries.
	c.	Gender is a confounder of the association between coffee drinking and dental caries.
	d.	Gender is neither a confounder nor an effect modifier of the association between coffee drinking and dental caries.