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HOSA > Types of Studies > Flashcards

Types of Studies Flashcards

1
Q

2 types of edpidemiologic studies

A

observational
experimental

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2
Q

Experimental Studies

A

an active attempt to change a disease determinant or the progress of a disease through treatment

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3
Q

what do major experimental study designs include?

A
  • randomized controlled trails,
  • field trials, (healthy participants)
  • community trials (ppl in the community)
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4
Q

randomized controlled studies (clinical trials)

A
  • designed to stude the effects of a particular intervention, usually a treatment for a specific disease
  • partients are alloved into groups randomly
  • ## should be comparable at the start of the investigation
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5
Q

Field Trials

A
  • involve healthy people who are presumed at risk
  • aimed at reducing exposure
  • often ligistically complicated and expensive
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6
Q

FIeld Trial groups

A

preventiatice intervention and no intervention (control group)

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7
Q

community trials

A

treatment groups are communities rather than individuals
- diseases that are influenced by social conditions
- prevention includes changing behaviours

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8
Q

Limitations of a community trials

A
  • small number of communitites can be involved
  • differences can be attributed to the study and not other factors
  • random isn’t always possible
  • difficult to isolate the general social change
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9
Q

Sources of Error

A
  • Random
  • Systematic
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10
Q

Random Errors

A

when the value of a sample measurement diverges from the true population value due to chance alone.

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11
Q

3 major sources of random errors

A
  • individual biological variation
  • sampling error
  • measurement error
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12
Q

individual biological variation

A

always occurs no measurement is perfectly accurate

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13
Q

Sampling Error

A

caused by the fact that a small sample is not representative of all the population’s variables
- increasing size can help, not necessarily

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14
Q

Measurement error

A

can be reduced by strict protocols and making individual measurements as precise as possible

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15
Q

What do you need to perform sample size calculations?

A
  • statistical significance to be able to tell the difference
  • acceptable error
  • magnitude of the effect
  • amount of disease
  • relative sizes
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16
Q

how many controls should you have for each case

A

more than four controls for each case

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17
Q

Systematic Error (or bias)

A

occurs when results differ in a systematic mannor from true values

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18
Q

high accuracy

A

a study with small systematic error, not affected by sample size

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19
Q

2 principle biases

A

selection bias
- measurement or classification bias

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20
Q

Selection Bias

A

a systematic difference between the characteristics of the people selected for a study and the characteristics of those who are not

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21
Q

Healthy Worker Effect

A

when the disease or factor under investigation makes people unavailable for the study

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22
Q

Measurement Bias

A

occurs when the individual measurements or classification of disease or exposure are inaccurate

  • dif labs cna get dif results
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23
Q

recall bias

A

occurs when there is a differential recall of information by cases and controls

participants don’t remember past things accurately.

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24
Q

blind study

A

investigators do not know how the participants are classified

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25
Q

double blind study

A

investigators and participantsand researchers do not know the treatment or intervention

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26
Q

Confounding

A

can occur when another exposure exists in the study population and is associated both with the disease and the exposure being studied.

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27
Q

methods of controlling confounding

A
  • randomization
  • restriction
  • matching
    analysis stage:
  • stratification
  • statistical modeling
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28
Q

Randomization to control confounding

A

the method for ensuring that potential confounding variables are equally distributed among the groups being compared.

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29
Q

Restriction to control confounding

A

limiting the study to people who have particular characteristics, limit such that confounding characterisitcs are not present in the sample

30
Q

Matching to control confounding

A

selecting study participants to ensure that potential confounding variables are evenly distributed in the two groups being compared, matching a person with a confounding variable to another.

31
Q

Stratification /Statistical Modelling to control confounding

A

used in large studies because it preferable than doing things during design

32
Q

Stratification

A

involves the measurement of the strength of associations in well defined and homogenous categories, if age is a confounding variable measure in age groups

33
Q

Statiscal modeling

A

range of statistical techniques

34
Q

validity

A

an expression of the degree to which a test is capable of measuring what it is intended to measure

valid = responds to the truth

35
Q

2 types of validity

A

internal validity
external validity

36
Q

Interval validity

A

the degree to which the results of an observation are correct for the partical group being studied

necessary but does not guarantee external validity

37
Q

External Validity

A

the exntent to which the results of a study apply to people or laborities not involved

  • external quality control
  • judgements
  • supported if similar results are found in studies in other populations
38
Q

Informed Consent

A

free and voluntary informed consent must be obtained, must retain the right to withdraw at any time

39
Q

an observational study

A

investigate measures, but it does not intervene

40
Q

2 types of observational studies

A
  • descriptive study
  • analytical study
41
Q

descriptive study

A

limited to a description of the occurrence of a disease in a population often the first step in an epidemiogic investigation

42
Q

analytical study

A

goes further by analysing relationships between bealth staus and other variables

43
Q

ecological studies

A

or correlational studies and useful for generating hypotheses, units of analysis are groups
- comparing different populations through time or place

44
Q

ecological fallacy

A

inaproriate conclusions fromt he study are drawn, the association observed at the group level does not reflect that at the individual level.

45
Q

Cross sectional studies or prevalence studies

A

measure of the prevalence of disease
measurements of exposure and effect are made at the same time
effect line follows exposure line there is a correlation

46
Q

Case-control studies

A

involves cases and suitable control group of people unaffect by the disease or outcome variable

47
Q

cases

A

people with a disease or other oucome variable of interest

48
Q

control group

A

the comparison of reference of the case group - healthy ppl

49
Q

Cohort studies

A

aka follow-up or incidence studies

begin with a group of people who are free of disease and who are classified into subgroups according to exposure to a potential cause of disease or outcome

50
Q

Nested Case-Control Studies

A

cases and controls are both chosen from a difined cohort

51
Q

risk =

A

attack rate

52
Q

risk among people who are exposed =

A

people with disease / total number of people exposed

53
Q

Risk among people not exposed

A

number of people with disease / total number of people not exposed

54
Q

Relative risk =

A

risk among people exposed / risk among people not exposed

55
Q

If relative risk >1

A

exposure and disease are positively associated (more exposed people have the disease)

56
Q

Relative risk = 1

A

exposure and disease are not associated

57
Q

relative risk <1 exposure

A

and disease are engatively associated (more unexposed people have the disease), those exposed are protected from the disease

58
Q

attributable risk =

A

risk of people exposed - risk of people not exposed

the proprtion of people who showed syptoms that can be credited to the exposure

59
Q

null hypothesis

A

the exposure is not related to the disease, is 1

60
Q

alternatie hypothesis

A

if the null hypothesis prove implausible, exposure IS associated with disease

61
Q

ODDS =/ probability

A
62
Q

odds calculation

A

number of times something happens/something DOES NOT happen

63
Q

probability calculation

A

number of times something happens/number of times something COULD happen

64
Q

case control calculations

A

odds

65
Q

Cohort calculations

A

risks

66
Q

odds ratio =

A

odds of disease among people exposed/odds ff disease among people not exposed

67
Q

if odds ratio >1

A

exposure and disease are positively associated - more diseased people exposed)

68
Q

if odds ratio = 1

A

exposure and disease are not associated

69
Q

if odds <1

A

exposure and disease are negatively associated, more non-diseased people are exposed

70
Q
A

HOSA (15 decks)

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