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1.
Consider studies designed to compare the occurrence of a binary outcome between two populations: population A and population B. In general, which of the following statements best describes the relationship between the relative risk estimate (RR_hat) and the odds ratio estimate (OR_hat) , both based on the same two samples from populations A and B?
a. RR_hat and OR_hat will always be exactly the same.
b. If RR_hat is greater than 1 then OR_hat will be less than 1.
c. RR_hat and OR_hat may differ in value, but will show the same direction of association.
d. RR_hat = OR_hat divided by the square root of (n1+n2), where n1 and n2 are the sizes of the samples from population A and population B, respectively
The correct answer is: c. RR_hat and OR_hat may differ in value, but will show the same direction of association.
Your Response: d. RR_hat = OR_hat divided by the square root of (n1+n2), where n1 and n2 are the sizes of the samples from population A and population B, respectively
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2.
How does the Kaplan-Meier approach to estimating the survival function utilize information from censored observations?
a. It does not. All censored observations are dropped from the data sample before the curve is estimated.
b. The Kaplan-Meier approach uses the censored observations when considering who is “at risk” of an event at a given time in the follow-up period. All censored observations are considered “at risk” of an event until the time of censoring.
c. The Kaplan-Meier approach treats the censoring times as event times. (i.e., it ignores the fact that these observations are censored).
d. The Kaplan-Meier approach treats the event times as censoring times.
The correct answer is: b. The Kaplan-Meier approach uses the censored observations when considering who is “at risk” of an event at a given time in the follow-up period. All censored observations are considered “at risk” of an event until the time of censoring.
Your Response: c. The Kaplan-Meier approach treats the censoring times as event times. (i.e., it ignores the fact that these observations are censored).
CORRECT
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3.
A randomized prospective study is conducted to estimate the association between taking a drug and relapse for patients with a specific type of cancer. The estimated incidence rate ratio of relapse for the treatment group relative to the placebo is 0.73. What is the proper interpretation of this value?
a. In a random sample of 10,000 persons from the same cancer population there would be 2,700 more relapses if these 10,000 persons took the drug as compared to if they did not take the drug.
b. In a random sample of 10,000 persons from the same cancer population there would be 2,700 fewer relapses if these 10,000 persons took the drug as compared to if they did not take the drug.
c. An individual (from the same cancer population) who takes the drug is 27% less likely to relapse as compared to an individual who has not taken the drug.
d. An individual (from the same cancer population) who takes the drug is 73% more likely to relapse as compared to an individual who has not taken the drug.
Your Response: a. In a random sample of 10,000 persons from the same cancer population there would be 2,700 more relapses if these 10,000 persons took the drug as compared to if they did not take the drug.
Feedback About Your Response:
Okay, given discrepancy between pdf and Quiz Generator answer choice C.
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4.
An article from the American Journal of Public Health reports the results from a randomized study designed to evaluate the efficacy of an intervention targeted to Hispanic/Latino men who identify as gay, bi-sexual or other men who have sex with men (MSM). A representative sample of 254 such men was randomized to be in either the intervention group (n=152) or the control group (n=152). The primary outcome under study getting tested for HIV within the six-months following group assignment (randomization) among those who had been sexually active in this same six-month follow-up period.
At six months of follow-up 141 subjects in the intervention group reported having had sex (with men and/or women) since randomization. Of these 141 men, 114 had been tested for HIV since being randomized.
At six months of follow-up 147 subjects in the control group reported having had sex (with men and/or women) since randomization. Of these 147 men, 40 had been tested for HIV since being randomized.
What is the (approximate) estimated relative risk of getting tested for HIV for subjects in the Intervention group compared to subjects in the Control group?
a. 11.3
b. 0.09
c. 3.0
d. 0.34
The correct answer is: c. 3.0
Your Response: a. 11.3
CORRECT
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5.
An article from the American Journal of Public Health reports the results from a randomized study designed to evaluate the efficacy of an intervention targeted to Hispanic/Latino men who identify as gay, bi-sexual or other men who have sex with men (MSM). A representative sample of 254 such men was randomized to be in either the intervention group (n=152) or the control group (n=152). The primary outcome under study getting tested for HIV within the six-months following group assignment (randomization) among those who had been sexually active in this same six-month follow-up period.
At six months of follow-up 141 subjects in the intervention group reported having had sex (with men and/or women) since randomization. Of these 141 men, 114 had been tested for HIV since being randomized.
At six months of follow-up 147 subjects in the control group reported having had sex (with men and/or women) since randomization. Of these 147 men, 40 had been tested for HIV since being randomized.
The difference in proportions of men being tested in the intervention group compared to the control group is 0.54 (54%). Suppose this intervention was used in a community with 1,000 Hispanic/Latino men who identify as gay, bi-sexual or other men who have sex with men (MSM). What would be the expected effect on HIV testing outcomes?
a. There would be an estimated 460 fewer men getting tested for HIV (in the six months following the intervention) than if the intervention was not given.
b. There would be an estimated 540 fewer men getting tested for HIV (in the six months following the intervention) than if the intervention was not given.
c. There would be an estimated 460 more men getting tested for HIV (in the six months following the intervention) than if the intervention was not given.
d. There would be an estimated 540 more men getting tested for HIV (in the six months following the intervention) than if the intervention was not given.
Your Response: d. There would be an estimated 540 more men getting tested for HIV (in the six months following the intervention) than if the intervention was not given.
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6.
A 2018 article in the New England Journal of Medicine reports the results from a randomized study designed to evaluate the association between following a Mediterranean diet plan (one of two types), and having a major cardiovascular event.
As per the researchers,
“In a multicenter trial in Spain, we assigned 7,447 participants (55 to 80 years of age, 57% women) who were at high cardiovascular risk, but with no cardiovascular disease at enrollment, to one of three diets: a Mediterranean diet supplemented with extra-virgin olive oil, a Mediterranean diet supplemented with mixed nuts, or a control diet (advice to reduce dietary fat). The primary end point was a major cardiovascular event (myocardial infarction, stroke, or death from cardiovascular causes). The median follow-up period was 4.8 years.”
The following Kaplan-Meier curves shows the estimated incidence of major cardiovascular events over the follow-up period separately for the two Mediterranean diet groups and the control group.
km curve
(Approximately) what percentage of subject randomized to the Mediterranean diet supplemented with mixed nuts (Med diet, nuts) did not have a major cardiovascular event within 3 years after being randomized to this group? (i.e survived beyond 3 years)
a. 2%
b. 3%
c. 97%
d. 98%
The correct answer is: d. 98%
Your Response: b. 3%
CORRECT
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7.
A 2018 article in the New England Journal of Medicine reports the results from a randomized study designed to evaluate the association between following a Mediterranean diet plan (one of two types), and having a major cardiovascular event.
As per the researchers,
“In a multicenter trial in Spain, we assigned 7,447 participants (55 to 80 years of age, 57% women) who were at high cardiovascular risk, but with no cardiovascular disease at enrollment, to one of three diets: a Mediterranean diet supplemented with extra-virgin olive oil, a Mediterranean diet supplemented with mixed nuts, or a control diet (advice to reduce dietary fat). The primary end point was a major cardiovascular event (myocardial infarction, stroke, or death from cardiovascular causes). The median follow-up period was 4.8 years.”
The following Kaplan-Meier curves shows the estimated incidence of major cardiovascular events over the follow-up period separately for the two Mediterranean diet groups and the control group.
km curve
Which of the following statements is true about the incidence rate ratio (IRR_hat) of having a major cardiovascular event(in the follow-up period for the Mediterranean Diet group (with nuts) compared to the Control Diet group (based on the results in the Kaplan-Meier curve)?
a. IRR_hat > 1
b. IRR_hat =1
c. IRR_hat < 1
d. IRR_hat should be “close” to 1, but there is no way to tell exactly how it will compare to 1.
Your Response: c. IRR_hat < 1
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8.
An article in JAMA: Psychiatry presents the results of a randomized controlled trial of Paliperidone Palmitate (Treatment) compared to Placebo for preventing relapse in patients diagnosed with schizophrenia. Patients were followed for up to 500 days after randomization, until relapse or censoring.
The risk of relapse in the follow-up period is summarized by randomization group in the following Kaplan-Meier curve. The vertical dashes on each curve represent censoring times.
km curve
Based on the Kaplan-Meier curve, what is the approximate 20th percentile of the time to-relapse distribution for subjects randomized to the placebo group?
a. 20 days
b. 400 days
c. 110 days
d. Percentiles cannot be estimated from a Kaplan-Meier curve
The correct answer is: c. 110 days
Your Response: d. Percentiles cannot be estimated from a Kaplan-Meier curve
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9.
An article in JAMA: Psychiatry presents the results of a randomized controlled trial of Paliperidone Palmitate (Treatment) compared to Placebo for preventing relapse in patients diagnosed with schizophrenia. Patients were followed for up to 500 days after randomization, until relapse or censoring.
The risk of relapse in the follow-up period is summarized by randomization group in the following Kaplan-Meier curve. The vertical dashes on each curve represent censoring times.
km curve
In the article, the authors report an incidence rate of 2.3 relapses/1,000 person-weeks for patients randomized to the enhanced prohylaxis group. This incidence rate (IR1) was calculated using data on all patients in the enhanced prohylaxis group, including both those who relapsed and those who were censored. Suppose, instead, the authors computed this incidence rate, but only used the data for patients in the enhanced prohylaxis group who relapsed while in the study (IR2) – in other words, the data on censored observations were ignored. How would IR2 compare in value to this reported incidence rate, IR1, of 2.3 relapses/1,000 person-weeks?
a. IR2 < IR1
b. IR2 > IR1
c. IR2 = IR1
d. IR2 will be similar in value to IR1, but there is no way to predict exactly how the two estimates will compare.
The correct answer is: b. IR2 > IR1
Your Response: a. IR2 < IR1
CORRECT
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10.
An article in JAMA: Psychiatry presents the results of a randomized controlled trial of Paliperidone Palmitate (Treatment) compared to Placebo for preventing relapse in patients diagnosed with schizophrenia. Patients were followed for up to 500 days after randomization, until relapse or censoring.
The risk of relapse in the follow-up period is summarized by randomization group in the following Kaplan-Meier curve. The vertical dashes on each curve represent censoring times.
km curve
In the Kaplan-Meier graph, why are the estimated curves for both groups (Treatment and Placebo) at 1 (100%) when time since randomization (the follow-up period) is 0 months?
a. Because 100% of the subjects relapsed at 0 months of follow-up.
b. Because 100% of the subjects were censored by the end of the study.
c. Because the follow-up period is less than 2 years.
d. Because all subjects followed in this study were event free (had not yet relapsed) at the beginning of the study
Your Response: d. Because all subjects followed in this study were event free (had not yet relapsed) at the beginning of the study
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11.
Data from the year 2015-16 National Health and Nutrition Examination Survey (NHANES) survey includes laboratory measurements on a random sample of more than four-thousand 18-65 year old persons in the United States. The following boxplots display the distribution of blood lead levels (mg/dL) for this sample, separately for males and females. The accompanying tables display summary statistics of the sample values.
BMI boxplots
Suppose you were able to take a random sample of 100 females from the same population of females as the sample of 2,128. How would the sample standard deviation estimate for these 100 sample blood lead level measurements (s_100) compare, in value, to the sample standard deviation of the original 2,128 blood lead level measurements (1.16 microgram/dL)?
a. s_100 > 1.16
b. s_100 < 1.16
c. s_100 will be exactly equal to 1.16
d. s_100 should be similar in value to 1.16, but there is no way to predict exactly how the two estimates will compare numerically
The correct answer is: d. s_100 should be similar in value to 1.16, but there is no way to predict exactly how the two estimates will compare numerically
Your Response: c. s_100 will be exactly equal to 1.16
CORRECT
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12.
Data from the year 2015-16 National Health and Nutrition Examination Survey (NHANES) survey includes laboratory measurements on a random sample of more than four-thousand 18-65 year old persons in the United States. The following boxplots display the distribution of blood lead levels (mg/dL) for this sample, separately for males and females. The accompanying tables display summary statistics of the sample values.
BMI boxplots
Which of the following best describes the shape of the lead level distributions in both sex groups?
a. Left-skewed
b. Symmetric
c. Right-skewed
d. Approximately normal
Your Response: c. Right-skewed
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13.
Data from the year 2015-16 National Health and Nutrition Examination Survey (NHANES) survey includes laboratory measurements on a random sample of more than four-thousand 18-65 year old persons in the United States. The following boxplots display the distribution of blood lead levels (mg/dL) for this sample, separately for males and females. The accompanying tables display summary statistics of the sample values.
BMI boxplots
What is the mean difference in blood lead levels for females compared to males?
a. 0.7 micrograms/dL
b. - 0.7 micrograms/dL
c. 0.45 micrograms/dL
d. - 0.45 micrograms/dL
The correct answer is: b. - 0.7 micrograms/dL
Your Response: c. 0.45 micrograms/dL
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14.
Data from the year 2015-16 National Health and Nutrition Examination Survey (NHANES) survey includes laboratory measurements on a random sample of more than four-thousand 18-65 year old persons in the United States. The following boxplots display the distribution of blood lead levels (mg/dL) for this sample, separately for males and females. The accompanying tables display summary statistics of the sample values.
BMI boxplots
Suppose, based on these results, researchers decide to make the cutoff for high blood lead levels at 4.6 micrograms/dL. A binary variable is created such that a value of 1 indicates that an individual’s blood lead level is greater than 4.6 micrograms/dL, and a value of 0 indicates that an individual’s HDL blood lead level is less than or equal to 4.6 micrograms/dL. What percentage of the males would have a value of 1 for this binary indicator? (you may assume there are no repeated values in these data)
a. 2.5%
b. 16%
c. 95%
d. 5%
The correct answer is: d. 5%
Your Response: b. 16%
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15.
Data from the year 2015-16 National Health and Nutrition Examination Survey (NHANES) survey includes laboratory measurements on a random sample of more than four-thousand 18-65 year old persons in the United States. The following boxplots display the distribution of blood lead levels (mg/dL) for this sample, separately for males and females. The accompanying tables display summary statistics of the sample values.
BMI boxplots
The relative risk of having high blood lead levels (greater than 4.6 micrograms/dL) for females compared to males is 0.60 What percentage of females have high blood lead levels?
a. 5%
b. 3%
c. 8%
d. This cannot be answered without using a standard normal table
The correct answer is: b. 3%
Your Response: c. 8%