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Flashcards in Research Designs Deck (53):
1

When an elderly sample is selected from a local fitness center

"Healthy-user" bias

2

When the population is selected from an impaired or diseased group

Berkson's Bias

3

When patients with certain characteristics are excluded

-Ex: racial groups, socioeconomic groups, etc

Exclusion Bias

4

Bias decreases

Generalizability

5

What are the two major classes of research designs?

1.) Experimental
2.) Non-experimental/observational

6

Is characterized by random assignment, manipulation of independent variables, and control of extraneous factors

Experimental Research

7

Experimental research is the best form of research for

Cause-and-effect

8

Experimental research is the standard for

Clinical trials

9

Characterized by no control over group assignment and no control over independent variables

Non-experimental/observational research

10

Non-experimental/observational research can not be used to determine

Causality

11

What is the gold standard experimental design for treatment studies?

Randomized control trial (RCT)

12

Equivalent groups are needed to interpret effects. We randomize because randomization removes

Selection bias

13

In the physicians aspirin study, randomization was accomplished through

Computer generated random numbers

14

When the investigator "knows" the expected results and treats groups differently

Investigator bias

15

One way to control investigator bias is when the people randomizing individuals into groups are blinded as to which subjects go into which group. This is called

Allocation Concealment

16

Another way to prevent investigator bias is to blind the investigator who is providing treatments or making measurements as to which group is which. This is called

Investigator blinding

17

Investigator bias can me minimized by

Allocation concealment and investigator blinding

18

When subjects change their behavior in a study, for example, they may want to please the investigators so they act differently. This is called

Subject bias (Hawthorne effect)

19

The Hawthorne effect (subject bias) effects

External and internal validity

20

How is the Hawthorne effect combated?

Subject "blinding" by use of a placebo group

21

Using a placebo group does not really work if the study involves an obvious

Physical change

22

When patients and clinicians are both blinded

Double Blinding

23

Ambiguous term, generally used to mean that the subjects are blinded

Single-blinding

24

Besides just controlling the allocation and outcome of a study, a researcher also needs to control

Extraneous variables (i.e. diet, non-compliance, drop out, etc.)

25

To help ensure compliance in the physicians study, subjects filled out a compliance questionnaire that also asked about the outcomes every

Six months

26

What are two ways to deal with drop-outs or treatment changes?

1.) Analysis according to treatment assigned (intention to treat)
2.) Analysis according to treatment received (explanatory) (better way)

27

The physicians study measured the number of new cases of disease arising during a given period of time, meaning they measured the

Incidence (absolute risk)

28

How do we find the Incidence (absolute risk)

Incidence = # people w/ disease / # total people

29

How do we calculate the relative risk or risk ratio?

incidence in exposed / incidence in unexposed

30

Both estimate the risk of disease (or outcome) in exposed (treated) vs. unexposed (untreated)

Risk ratios and Odds ratios

31

What is the risk reduction?

1 - RR

32

The physicians study showed a reduction in the risk of MI by

47%

33

However, the physicians study also showed an INCREASE in the risk for

Strokes

34

What are two common types of observational studies?

Case-control and cohort studies

35

What makes case-control and cohort studies observational?

1.) Can not manipulate independent variables
2.) Can not control all extraneous factors

36

A group of people who have something in common when they are first assembled and who are then observed for a period of time to see what happens to them

Cohort

37

The goal of this type of study is to study "predictor variables"

Cohort (incidence) Studies

38

One of the problems with cohort studies may be

Internal validity

39

What is a major threat to the internal validity of a cohort study?

Extraneous factors

40

Differences between groups, i.e. another factor (other than the one of interest) that may be related to the differences between groups

Extraneous factors

41

The best solution to the threat that extraneous factors pose on internal validity is

randomization

42

To help minimize the extraneous factors, we could increase restriction, increasing restriction decreases

Generalizability (external validity)

43

What are the two different types of cohort studies?

Prospective and Retrospective

44

What is the usual statistic when comparing two groups?

Risk Ratio (RR = Incidence in exposed / Incidence in unexposed)

45

Like odds, Risk Ratios (RRs) are given with 95% confidence intervals. If the confidence interval includes 1, there is

No statistically significant difference

46

Looking backwards to compare people with and without a condition

Case-control study

47

Case-control studies are good for

Diseases w/ long latency and rare diseases

48

The big difference between case control and cohort studies is that in case-control studies, we don;t measure the

Incidence (it can only be estimated)

49

Measure how many people develop disease out of a total, i.e. what is the relative incidence of disease in both groups

Cohort studies

50

Look at people who already have the disease and determine the odds of exposure. I.e. what is the odds that the diseased group was exposed?

Case-control studies

51

What are three threats to the internal validity in case-control studies?

1.) Control group selection
2.) Recall bias
3.) Can't determine risk directly

52

People may not remember their exposure of the event of interest. This is called

Recall bias

53

Since case-control studies can not measure the incidence, they instead use the

Odds ratios

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