Epi/Biostats

Question 1

Cross-sectional Study

Answer 1

observational
assesses frequency of disease at a particular point in time
measures disease prevalence

Question 2

Case-control Study

Answer 2

observational
compares group with disease to a group without disease to look for exposure
measures odds ratio

Question 3

Cohort Study

Answer 3

observational
compares group with exposure that without
measures relative risk
prospective OR historical

Question 4

Twin Concordance Study

Answer 4

compares frequency of disease in MZ or DZ twins

nature vs nurture

Question 5

Adoption Study

Answer 5

compares siblings with bio vs adoptive parents

nature vs nurture

Question 6

Phase I clinical trial

Answer 6

small # healthy volunteers

safety, tox, PK, PD

Question 7

Phase II clinical trial

Answer 7

small # of pts with disease

efficacy, dosing, AE

Question 8

Phase III clinical trial

Answer 8

Large # of pts, random assignment

compare to standard therapy

Question 9

Phase IV clinical trial

Answer 9

post-marketing surveillance

AE

Question 10

Sensitivity

Answer 10

True Positive Rate=TP/(TP+FN)
probability of a positive test when the disease is present
high = low FN rate
SN-N-OUT (highly SeNsitive test, when Negative, rules OUT disease)

Question 11

Specificity

Answer 11

True Negative Rate=TN/(TN+FP)
probability of a negative test when the disease is absent
high=low FP rate
SP-P-IN (highly SPecific test, when Positive, rules IN disease)
confirm after + screening test

Question 12

Positive predictive value

Answer 12

PPV=TP/(TP+FP)
probability that a person with a + test actually has the disease
varies directly with disease prevalence

Question 13

Negative predictive value

Answer 13

NPV=TN/(TN+FN)
probability that a person with a - test actually does not have the disease
varies indirectly with disease prevalence

Question 14

Incidence

Answer 14

# of new cases/# at risk
during a specified time period

Question 15

Prevalence

Answer 15

# of existing cases/total#
at a point in time

Question 16

Odds ratio

Answer 16

odds that the group with the disease was exposed to a RF divided by the odds that the group without the disease was exposed

Question 17

Relative Risk

Answer 17

Risk of developing disease in the exposed group divided by risk in the unexposed group
equals OR at low prevalence

Question 18

Attributable Risk

Answer 18

Difference in risk between exposed and unexposed groups

the proportion of disease occurrences that are attributable to the exposure

Question 19

Relative Risk Reduction

Answer 19

the proportion of risk reduction attributable to the intervention as compared to a control
RRR=1-RR

Question 20

Absolute Risk Reduction

Answer 20

difference in risk attributable to the intervention as compared to a control

Question 21

Number Needed to Treat

Answer 21

NNT=1/ARR
# of patients who need to be treated for 1 pt to benefit

Question 22

Number Needed to Harm

Answer 22

NNH=1/AR
# of patients who need to be exposed to a RF for 1 pt to be harmed

Question 23

Precision

Answer 23

consistency, reproducibility, reliability
absence of random variation (SD)
increases power

Question 24

Accuracy

Answer 24

trueness, validity

absence of systematic error or bias

Question 25

Selection Bias

Answer 25

error in recruiting and assigning subjects | may correct with randomization

Question 26

Recall Bias

Answer 26

awareness alters recall by subjects | common in retrospective studies

Question 27

Measurement Bias

Answer 27

distorted info gathering | correct with standardized testing

Question 28

Procedure Bias

Answer 28

subjects in different groups are not treated the same | can correct with blinding and placebo use

Question 29

Observer-expectancy bias

Answer 29

when the researcher believes the treatment is efficacious | use blinding and placebo

Question 30

Confounding bias

Answer 30

when a factor is related to both exposure and outcome but not in same causal path can match or randomize

Question 31

Lead-time bias

Answer 31

early detection is confused with increased survival

Question 32

Normal distribution

Answer 32

68% between 1 SD either side of mean 95% between 2 SD 99.7% between 3 SD

Question 33

Type I error (alpha)

Answer 33

stating that there is a difference when none exists incorrectly reject the null hypothesis False-positive error alpha level

Question 34

Type II error (beta)

Answer 34

the null hypothesis is not rejected when it is false stating that there is not a difference when one exists false-negative error

Question 35

Power

Answer 35

1-beta probability of rejecting the null when it is false increases with sample size, expected effect size, and precision

Question 36

Confidence Interval

Answer 36

range of values within which the true mean falls CI=mean+/-Z(SEM) 95% CI for p=0.05

Question 37

t-test

Answer 37

difference between means of 2 groups

Question 38

ANOVA

Answer 38

differences between means of 3 or more groups

Question 39

Chi-square

Answer 39

differences between 2 or more proportions of CATEGORICAL outcomes