Epidemiology

Question 1

Which study design is the most scientifically sound and the best measure of exposure?

Answer 1

Clinical trial

Question 2

Which study design is the most accurate observation study and a good measure of exposure?

Answer 2

Cohort study

Question 3

Which study design can study rare diseases and is relatively less expensive/fast?

Answer 3

Case-control

Question 4

Which study design is the fastest and least expensive and measures multiple exposures and outcomes?

Answer 4

Cross-sectional

Question 5

Which study design is time consuming and the most expensive?

Answer 5

Cohort study

Question 6

Which study design causes possible time-order confusion and possible error recalling exposures?

Answer 6

Case-control

Question 7

Which study design causes possible time-order confusion, the least confidence in findings, and measurement bias?

Answer 7

Cross-sectional

Question 8

Which study design is time consuming, not generalizable, unethical for harmful exposures, and most expensive?

Answer 8

Clinical trial

Question 9

What happens to incidence and prevalence if a new effective treatment is initiated?

Answer 9

Incidence stays the same, prevalence decreases

Question 10

What happens to incidence and prevalence if a new effective vaccine gains widespread use?

Answer 10

Incidence decreases, prevalence decreases

Question 11

What happens to incidence and prevalence if number of persons dying from the conditions decreases?

Answer 11

Incidence stays the same, prevalence increases

Question 12

Case fatality rate equation

Answer 12

Number of deaths due to disease/number of cases of a disease

Question 13

Proportionate mortality rate equation

Answer 13

Number of deaths due to disease/total deaths in the population

Question 14

Attributable risk equation

Answer 14

Incidence rate among exposed - incidence rate among unexposed

Question 15

Relative risk equation

Answer 15

Incidence rate among treated / incidence rate among non-treated

Question 16

Attributable risk percent equation

Answer 16

AR / incidence rate among treated

Question 17

Number needed to treat

Answer 17

1 / attributable risk

Question 18

Relative risk equation

Answer 18

[a/(a+b)] / [c/(c+d)]

Question 19

Odds ratio equation

Answer 19

ad/bc

Question 20

T/F: For a rare disease, odds ratio is a good measure of the relative risk.

Answer 20

True

Question 21

Interpret a RR of 5.0

Answer 21

50% chance of developing a disease if exposed

Question 22

P value of 0.05. What does this mean?

Answer 22

There is a 5% chance that the results were just do to chance

Question 23

Limitations of p-values

Answer 23

dependent on sample size
larger effect sizes more likely to produce significant sample size
only assess the null hypothesis, not the alternative hypothesis
tells us about statistical significance but nothing about magnitude of effect

Question 24

T/F: P-values more likely to be statistically significant for larger effects

Answer 24

True.

Question 25

Reject null hypothesis when it is, in fact, true.

Answer 25

Type I error. Convicting someone who is innocent.

Question 26

Failing to reject the null hypothesis, when in fact, it is false.

Answer 26

Type II error. Acquit someone when they are guilty.

Question 27

When odds ratio overestimates relative risk, what type of error is this?

Answer 27

Type I

Question 28

The probability that a person with a positive result actually has the disease

Answer 28

Positive predicted value

Question 29

The probability that a person with a negative result actually does NOT have the disease

Answer 29

Negative predicted value

Question 30

Equation for positive predicted value

Answer 30

PPV = True positives/(True positives + False positives)

Question 31

Equation for negative predicted value

Answer 31

NPV = True negatives/(TN+FN)

Question 32

If the prevalence increases, does PPV increase or decrease? What about NPV?

Answer 32

It increases! And Negative predicted value decreases…

Question 33

What is selection bias?

Answer 33

Choosing participants for a study who are most qualified to provide the results you are looking for.
Is the level of exposure in the controls the level expected in the population?

Question 34

What is confounding by indication?

Answer 34

A bias frequently encountered in studies of drug effects. Because the allocation of treatment is not randomized and the indication for treatment may be related to the risk of future health outcomes, there are different risks for treated vs untreated groups, which can generate biased results
Ex: drug given to highly selected individuals who needed the drug because of their poor prognosis

Question 35

What causes recall bias?

Answer 35

caused by differences in the accuracy or completeness of the recollections retrieved (“recalled”) by study participants regarding events or experiences from the past. Ex: case vs control mothers may recall differences in exposures.

Question 36

How is a confounding factor similar to “guilt by association.”

Answer 36

If you fail to account for a confounding factor, you may develop a perceived relationship between an independent variable and a dependent variable that has been misestimated

Question 37

A logical fallacy in the interpretation of statistical data where inferences about the nature of individuals are deduced from inference for the group to which those individuals belong

Answer 37

Ecological falacy

Question 38

Interpretation and limitations of P-value: interpretation

Answer 38

Interpretation: % of random variability; limitation: large sample size gives skewed p-value

Question 39

(blank) (exposure before disease) is a strength of clinical trials and cohort studies

Answer 39

Temporality