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Flashcards in Biostatistics Deck (33):
1

Case control study
a. Compares what?
b. Looks for what?
c. Measured by?
d. Asks what?
e. Retrospective or Prospective?

a. Compares a group of people WITH disease to group of people WITHOUT disease
b. Looks for prior exposure or risk factor
c. Measured by odds ratio
d. Asks "what happened?"
e. Retrospective and observational

2

Cohort study
a. Compares what?
b. Looks for what?
c. Measured by?
d. Asks what?
e. Retrospective or Prospective?

a. Compares a group of people with a given exposure or risk factor to a group without such exposure.
b. Looks to see if exposure increases the likelihood of disease
c. Measured by relative risk
d. Asks either "Who will develop disease?" or "Who developed the disease?"
e. Can be retrospective or prospective

3

What is odds ratio?

Odds that the group with the disease (case) was exposed to a risk factor divided by the odds that the group without the disease (controls) was exposed; odds ratio

4

What is relative risk?

Risk of developing disease in the exposed group divided by risk in the unexposed group; relative risk

5

Cross-sectional study
a. Design?
b. Asks what?
c. Measures what?

a. Collects data from a group of people to assess frequency of disease (or risk factor) at a particular point in time.
b. What is happening?
c. Disease prevalence

6

Twin concordance study
a. Design?

a. Compares the frequency with which both monozygotic twins and both dizygotic twins develop the same disease

7

Adoption study
a. Design?

a. Compares siblings raised by biological vs. adoptive parents

8

Phase I Clinical Trial
a. Typical study sample
b. Purpose

a. Small number of healthy volunteers (medical students)
b. "Is it safe?" Assesses safety, toxicity, pharmacokinetics, pharmacodynamics

9

Phase II Clinical Trial
a. Typical study sample
b. Purpose

a. Small number of patients with disease of interest
b. "Does it work?" Assesses treatment efficacy, optimal dosing, adverse effects

10

Phase III Clinical Trial
a. Typical study sample
b. Purpose

a. Large number of patients randomly assigned either to treatment under investigation or best available treatment
b. "Is it as good or better?" Compares new treatment to the current standard of care

11

Phase IV Clinical Trial
a. Typical study sample
b. Purpose

a. Postmarketing surveillance of patients after treatment is approved
b. "Can it stay?" Detects rare or long-term adverse effects. Can result in treatment being withdrawn from market

12

Sensitivity equation

True positives/True positives + False negatives OR
1 - false negative rate

13

Specificity equation

True negatives/True negatives + False positives OR
1 - false positive rate

14

PPV equation

True positives/ True positives + False positives

15

NPV equation

True negatives/ True negatives + False negatives

16

Odds ratio equation

(A/B)/(C/D)

17

Relative risk equation

A/(A+B) / C/(C+D)

18

Attributable risk

A/(A+B) - C/(C+D)

19

Absolute risk reduction

C/(C+D) - A/(A+B)

20

Relative risk reduction

1 - RR

21

Number Needed to Treat

1/ARR

22

Number Needed to Harm

1/AR

23

What is precision?

Consistency and reproducibility of a test (reliability)

24

What is accuracy?

Trueness of test measurements (validity)

25

What is selection bias?

Error in assigning subjects to a study group resulting in an unrepresentative sample; most common a sampling bias

26

Berkson bias?

Study population selected from hospital is less healthy than general population

27

Recall bias?

Awareness of disorder alters recall by subjects, common in retrospective studies

28

Sampling bias?

Study population does not accurately represent the target population

29

Late-look bias?

Results from info being gathered too late to accurately sample entire population

30

Procedure bias?

Subjects in different groups are not treated the same

31

Lead-time bias?

Early detection is confused with increased survival

32

Observer-expectancy bias? (Pygmalion effect)

Researcher's beliefs in the efficacy of a treatment changes the outcome of that treatment - self-fulfilling prophecy

33

Confounding bias?

When a factor is related to both the exposure and outcome but not on the causal pathway --> factor distorts or confuses effect of exposure on outcome
-Pulmonary disease is more common in coal workers than general population BUT people who work in coal mines also smoke more frequently than the general population