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Flashcards in Study Design Deck (69)
1

goals of epidemiological studies

describe disease

identify associations

2

a good study is:

scientifically sound

valid

precise

efficient

3

descriptive study designs

not comparing groups

case reports
case series
cross-sectional descriptive studies

4

analytical study designs

groups are compared

experimental
observational

5

analytical study: experimental

clinical trials (treated/exposed)

6

analytical study: observational

compare groups of populations- ecological

compare groups of individuals- cross-sectional analytical studies, case-control, cohort (prospective and retrospective)

7

characteristics of descriptive studies

describe disease

no hypothesis is tested

no groups compared

8

characteristics of analytical studies

determine if there is an association and if so the strength

designed to test hypothesis

always compares groups

9

descriptive study: 1 subject

case report

10

descriptive study: a few subjects (6-12)

case series

11

descriptive study: lots of subjects (several dozen to hundreds)

descriptive cross sectional

12

disadvantages of case reports and case series

small number of cases

findings are not generalizable to the population

strictly descriptive

13

disadvantages of case reports and case series

small number of cases

findings are not generalizable to the population

strictly descriptive

14

descriptive cross-sectional study

sample of population

estimate the amount and distribution of disease

measure of disease occurrence is usually prevalence

15

steps of descriptive cross-sectional study

select subjects from the source population

measure the disease i each study subject

calculate the measure of disease occurrence

16

advantages of descriptive cross-sectional study

can generalized to the population

fast and cheap

provide good descriptive or baseline data for future

17

disadvantages of descriptive cross-sectional study

not good for causality

prevalence is of limited value

18

what is an association

when one changes so does the other

exposure and outcome are dependent on one another

19

outcome

a result or response, usually a disease or some other change in health status

20

exposure

potential determinant of disease or health status

21

T/F an exposure may increase, decrease, or have no effect at all

true

22

determinant (risk factor)

once an exposure is shown to be associated with disease

23

T/F analytical studies compare groups on the basis of either exposure or outcome

true

24

T/F controls are essential for measuring the effect of exposure

true

25

T/F controls are the reference group

true

26

how are analytical groups compared

exposure or outcome

27

observational studies

observes real life situations and draw inferences from them

not given a treatment or exposure

28

experimental studies

investigator manipulates subjects

subjects are selected and the allocated to receive a treatment or an exposure

29

selected

subjects selected because of their characteristics

30

allocated

assigned- experimental studies only

located to receive a treatment or exposure in order to study the effect

31

subjects selected because..

represent a population

exposure status

outcome status

32

randomization

process of making something random

each subject has an equal chance of being selected or allocated

33

sampling

subset of a population/group

goal is to select sample to represents population or group studies

34

T/F in experimental studies subjects randomly allocated to groups

true

35

experimental studies as also known as

randomized control trials
clinical trials

36

T/F experimental studies can be done in the lab or field

true

37

advantages of experimental studies

may establish causality

well-controlled studies are essential free of bias and confounding

statistically powerful

exposures and outcomes are clearly measured during the study

38

disadvantages of experimental studies

expensive and very narrow in scope

not always ethical

placebo effect

loss of follow-up can be higher for some treatments

39

T/F in observational studies are selected to participate in the study and then classified into groups

true

40

what are 2 broad types of observational designs

populations
individuals

41

ecological study designs

compares groups of populations

42

T/F no measurements are made on individuals-all measured at a population level

true

43

steps in ecology study

select a sample of populations

find population-level statistics on exposure and outcome for each population

compare groups of populations

44

T/F exposure and outcome are not measured at an individual level, but at the population level

true

45

advantages of ecological study design

can be done quickly and inexpensively

analysis and interpretation are relatively simple

can assess a wide range of exposure levels

46

disadvantages of ecological study design

ecologic fallacy

cannot detect subtle of complicated relationships

47

what is an ecologic fallacy

relationship observed at the population level may not hold true at the individual level

48

observational study on individuals

based on reason for selecting study subjects: represent a populations, have a certain outcome or exposure

49

analytical cross-section studies

individuals selected to represent a population

only selected one

50

T/F analytical cross-section studies measure both exposure and outcome (usually at the same time)

true

51

advantages of analytical cross-sectional studies

can generalize to population

fast and cheap

provide good descriptive or baseline data for future studies

52

disadvantages of analytical cross sectional studies

not good for causality

prevalence is limited (disease of long duration will have high prevalence even if incidence is low)

53

T/F diseases of short duration and high mortality will be under-represented in an analytical cross-sectional study

true

prevalence is limited in nature

54

case-control studies

individuals are selected to represent outcome

selected because of outcome status

55

T/F with case-control studies there is an association if the amount of exposure is different between the 2 outcome (disease) groups

true

number of subjects with the exposure are counted in each outcome and compared

56

selection in case-control studies

selection of cases

selection of controls

57

case definition

clearly describes and defines cases of the disease of interest

58

advantages of case control studies

short timeline

can look at multiple risk factors at one time

good for studying rare disease

59

disadvantages of case-control studies

poor selection of control can invalidate entire study

depends on accurate assessment of exposures that happened in the past

60

cohort studies

selected to represent exposure groups

used to study the effect of an exposure

61

what are they two types of cohort studies

prospective
retrospective

62

prospective cohort

forward in time

subjects selected based on exposure status and then followed over time to see if they develop the outcome

63

measure of association for prospective cohort

relative risk

64

retrospective cohort

back in time

selected based on exposure status, then outcome is determined from history, records, questionnaires, tests etc to determine if had/have outcome

65

measure of association for retrospective cohort

prevalence ratio (disease has already occurred)

66

advantages of prospective cohort studies

better to establish causality

can look at multiple exposures at one time

good for studying rare exposures

67

disadvantages of prospective cohort studies

can take a long time

have to deal with changing study populations

depends on accurate assessment of exposures and consistent assessment over time

68

advantages of retrospective cohort study

short timeline

can look at multiple exposures at one time

good for rare exposures

69

disadvantages of retrospective cohort studies

not as good for establishing causality

poor selection of controls can invalidate the entire study

depends upon accurate assessment of diseases that happened in past