Question 1

When the Breslow-Day test results in a significant p-value

Accepted Answer

A)   The estimated odds ratios are different.
B)   The estimated odds are different.
C)   The estimated relative risks are different.
D)   The estimated risks are different. A

Question 2

Which of the following represents an odds ratio in a logistic regression?

Accepted Answer

A)   estimate of b
B)   logit difference (logit=log(odds) ) 
C)   exp(b) 
D)   exp(logit)  C

Question 3

Given that an interaction effect is found significant in the logistic regression model, the main effects associated with the interaction should NOT be interpreted independently. Why? What should be reported/interpreted when an interaction is present?

Accepted Answer

The effect of the explanatory variable on the outcome depends on both the main effect and the interaction effect. Thus, the odds ratio estimates should be calculated and interpreted for each level of the effect modifier.

Question 4

The plot below presents the odds ratio estimates and 95% confidence intervals from three different studies. Interpret.

Accepted Answer

The answer of The plot below presents the odds ratio...

Question 5

What is the rationale behind using logit (log(odds)) and not odds or probability of the event as the outcome variable in logistic regression?

Accepted Answer

The answer of What is the rationale behind using logit...

Question 6

Briefly explain what a positive and negative parameter estimate (b) implies in a logistic regression in terms of the probability of the outcome.

Accepted Answer

The answer of Briefly explain what a positive and negative...

Question 7

Which of the following characterizes a good screening test?

Accepted Answer

A)   high sensitivity and high specificity
B)   high sensitivity and low specificity
C)   low sensitivity and high specificity
D)   low sensitivity and low specificity

Question 8

If the global null hypothesis "All of the true slopes are 0" is rejected, what can be concluded?

Accepted Answer

The answer of If the global null hypothesis "All of...

Question 9

Which of the following is a logistic regression model? (p=probability of an event)

Accepted Answer

A)   p=a+b1x1+ · · · +bkxk
B)   p/(1-p) = a+b1x1+ · · · +bkxk
C)   log(p) = a+b1x1+ · · · +bkxk
D)   log(p/(1-p) ) = a+b1x1+ · · · +bkxk

Question 10

Which of the following is an appropriate way to handle a confounder?

Accepted Answer

A)   adjustment
B)   stratification
C)   group matching
D)   all of the above

Question 11

Three diagnostic tests (Pearson, Deviance, Hosmer-Lemeshow) can be used to evaluate the model fit of logistic regression. Provide the null hypothesis for a test of model fit. What would you conclude if the hypothesis is not rejected?

Accepted Answer

The answer of Three diagnostic tests (Pearson, Deviance, Hosmer-Lemeshow) can...

Question 12

The Mantel-Haenszel's odds ratio is often used to account for confounding. When a confounding variable is found to be an effect modifier, why is it not appropriate to report Mantel-Haenszel odds ratios?

Accepted Answer

The answer of The Mantel-Haenszel's odds ratio is often used...

Question 13

How does the magnitude of the parameter estimate (b) in a logistic regression influence the interpretation of the risk factor?

Accepted Answer

The answer of How does the magnitude of the parameter...

Question 14

ROC curves are often used to evaluate model fit for a logistic regression. Why is this appropriate?

Accepted Answer

The answer of ROC curves are often used to evaluate...

Question 15

In a body mass index (BMI) test, a cutoff point is established such that an individual is classified as obese when test score is above the cutoff point. As the cutoff score increases, how will the sensitivity and specificity of the test change?

Accepted Answer

The answer of In a body mass index (BMI) test,...

Question 16

Which (A, B, or C) represents the best screening test? Why? What does curve C tell about the screening test?

Accepted Answer

The answer of Which (A, B, or C) represents the...

Question 17

Which of the following yields the correct estimated odds ratio for a 5-unit increase in an explanatory variable?

Accepted Answer

A)   5b
B)   exp(5b) 
C)   5exp(b) 
D)   exp(5) (exp(b) )

Question 18

List situations when Mantel-Haenszel's method for calculating an adjusted odds ratio is no longer appropriate. What type of analysis is an alternative in these situations?

Accepted Answer

The answer of List situations when Mantel-Haenszel's method for calculating...

Question 19

Define sensitivity and specificity.

Accepted Answer

The answer of Define sensitivity and specificity....

Question 20

Suppose that the estimated odds ratio of asthma is reported to be 0.45 (95% CI: 0.1, 0.8) for children living near farms (measured in kilometers, km), adjusting for age, race, and sex. Interpret.

Accepted Answer

The answer of Suppose that the estimated odds ratio of...

Exam 5: A Dichotomous Outcome: Confounding and Regression