# Lecture 5 and 7 (Study Types) Flashcards

1

Q

Cohort study definition:

A

- prospective, observational.
- start with no diseases, look at exposure and disease development over time.
- more expensive than case-control.

2

Q

Statistic utilized for cohort study:

A

RELATIVE RISK

3

Q

Cross-sectional study definition:

A

- single time point, observational.
- take a slice of the population

- how many people have a disease or a risk factor right now

4

Q

Statistic for cross-sectional study:

A

POINT PREVALENCE

**point prevalence = (total #sick)/(total population)**

5

Q

Case-control study definition:

A

- retrospective, observational.
- start with disease and go back retrospectively to find the risk factor
- cheaper than cohort studies

6

Q

Statistic for case-control study:

A

ODDS RATIO

7

Q

Nested case-control study definition:

A

- select cases and controls from a cohort study
- go back and find the risk factor

8

Q

The three types of error in studies:

A

- random (chance)
- systematic (bias)
- confounders

9

Q

Random error:

A

- chance
- will cancel out as sample gets larger
- more likely will lead to type 2 error

10

Q

Systematic error (bias):

A

- cannot be corrected for regardless of sample size
- more likely will lead to a type 1 error

11

Q

Confounder definition:

A

- must be associated with exposure
- must be associated with outcome
- cannot be in the causal pathway between exposure and outcome

12

Q

How can you control for confounding?

A

- At the design stage:
- randomization
- restriction
- matching

- At the analysis stage:
- stratification
- multivariable adjustment (regression)

13

Q

Selection bias:

A

- nonrandom assignment to groups
- loss to follow up
- must be controlled at design stage.

14

Q

Healthy worker effect (bias):

A

- workers are generally healthier than the general population.

15

Q

Self-selection bias:

A

- research volunteers different from the general population in terms of their exposure and disease status.

16

Q

Withdrawal bias:

A

- differential loss to follow-up; people drop out
- drop outs may be more sick

17

Q

Recall bias:

A

- knowledge of presence of disease changes subject’s response