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Poph192 > 22-28 lectures > Flashcards

22-28 lectures Flashcards

1
Q

what are the 4 catagories that chance is divided into?

A

validity
sampling error
confidence intervals
p-values

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2
Q

what is validity split into?

A

internal and external validity

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3
Q

what is internal validity?

A

we need to consider chance, bias and confounding
its when we ask are there other explanations for the study findings, apart from them being right

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4
Q

what is external validity?

A

the extent to which the study findings are applicable to a broader or different population

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5
Q

how do we estimate the parameters of the actual prevalnce/incidence/RR/OR/RD?

A

we you the data from a study population parameters to take an estimate

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6
Q

what is sampling errors?

A

when samples would be quite different to the others samples and this is up to chance and is refferend to as sampling error

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7
Q

how do we reduce chance?

A

we can increase the number of samples in the study which reduces sample variablity and increases the likelihood of getting a represtative sample and increases the percision of the parameters

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8
Q

what percentage is confidence intervals?

A

95%

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9
Q

what does the 95% confidence intervals represent?

A

the range of values within which the parameter will lie 95% of the time if we continue to repeat the same study with new samples

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10
Q

where are our odds ratio found?

A

between our 2 confidence intervals

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11
Q

what can we use the 95% confidence intervals help us with?

A

to make predictions where our prevalence and OR will fall
tell us whether the study findinhgs are clinically important

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12
Q

what are parameters?

A

the true value of the measure in the population that the study is trying to recover

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13
Q

what is the point estimate?

A

the measure found in the sample study

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14
Q

what are p-values?

A

the possability of getting estimate when there is no association just because of sampling error (chance)

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15
Q

if the p-value possibility is really low then what?

A

it is unlikely to be that the estimate is due to sampling error (chance)

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16
Q

what is H0?

A

the null hypothesis

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17
Q

what is the null hypothesis?

A

there is no association in the population so the RR,OR = 1 and the RR = 0

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18
Q

what is Ha?

A

alternative hypothesis

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19
Q

what is the alternative hypothesis?

A

when the parameter does not equal the null value so the RR, OR doesnt equal 1 and RD doesnt equal 0

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20
Q

what is statisical significance?

A

the threshold we set because of sampling error (type-1 error)

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21
Q

what happens if the p less than 0.05?

A

then we reject H0 and accept Ha so association is not statistically significant

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22
Q

what happens if the p is grater than 0.05?

A

then we fail to reject H0 and reject Ha so the association is significantly significant

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23
Q

what can no association be beacause?

A

chance

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24
Q

what if we dont have association of the true (unknown) and association of study results?

A

then we have a type-1 error

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25
Q

what if we have association of the true (unknown) and not the association of the study results?

A

then we have a type-ll error

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26
Q

what are type-ll errors?

A

incorrectly rejection of H0 when it shouldve been

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27
Q

what causes type-ll errors?

A

due to having too few people in the study

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28
Q

how to we not get type-ll errors?

A

by having a bigger sample size to have a smaller p- value

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29
Q

what happens if the CI include the null value?

A

the p-value is greater that 0.05 so it is not statistically significant

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30
Q

what happens if the CI doesnt include the null value?

A

then the p-value is less than 0.05 so it is statistically significant

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31
Q

what is CI?

A

confidence interval

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32
Q

what are limitations of the p-value?

A

arbitrary threshold
only about H0
nothing about importance

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33
Q

what is arbitrary threshold?

A

the statistical significance threshold is arbitrary and artificial
its useful for reporting p-values rather than just the statistical significance

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34
Q

what is only about H0?

A

just giving evidence about consistancy with the null hypothesis
not really percise

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35
Q

what is nothing about importance?

A

statistical significance is not clinical significance
does not say that the results of the study are valid useful or correct

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36
Q

what is bias?

A

a systematic error in an epidemiologic study that results in an incorrect estimate of the association between exposure and risk of a disease

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37
Q

what is random error?

A

something that doesnt really have a pattern with it

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38
Q

what is sytematic error?

A

iif there is a pattern that we cant change no matter the amount of samplinh that we do

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39
Q

what can systematic error be?

A

an over-estimation
an under estimation
not affected

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40
Q

when is selection and information bias collected?

A

can only be controlled during the design and data collection phases of a study

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41
Q

what are 3 potential sources of bias when collecting data?

A

selection bias
information bias
publication bias

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42
Q

What is selection bias?

A

who is going to be in the study

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43
Q

when does systematic bias occur?

A

when the systematic difference between the people who are included in the study and those who are not, or when study and comparison groups are selected inappropriately or using different criteria

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44
Q

where is there systematic difference?

A

between those who are included and those who are not included

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45
Q

what is recruitment?

A

how people can get recruited into the epidemiology study one way is an ad for people to notice

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46
Q

what is random selection?

A

better at giving us a better representation for there to be minimised bias course

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47
Q

what do people who dont agree to participate and can lead to?

A

systematuic error

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48
Q

why do we want to maximise the response rate?

A

because the difference of people who are in the investigation and who isnt can lead to a negative affect on the data

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49
Q

what can minimise the amount of people from dropping out?

A

following up

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50
Q

what are some ways to minimise lose to follow up?

A

-alternative contract details obtained at the start of the study
-maintaining regular contact
-making several attempts to contact people

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51
Q

what are cross sectional study designs?

A

the exposures and outcomes are assessed at one point of time and we can measure the prevalence of the study

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52
Q

when is comes to bias in cross sectional study designs what do we have to consider?

A

who entered the study
sample represntative of source population
what is the response rate

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52
Q

what happenns if the selection is dependant on their outcome status in case controlled studies?

A

exposure and outcome have already occurred
cases and controls are selective separately

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52
Q

what are case controlled studies?

A

the cases and controls goes to the measure past exposure when considering bias

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53
Q

what is the MOA in a protective factor?

A

underestimated beacsue of bias the measure of association is under estimated and the value is towards the null but estimation is bias numerically upwards

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53
Q

what is the MOA in a harmful factor?

A

underestimated because of bias the measure of association is under estimated and is numerically downwards

53
Q

what are participatants in cohort studies?

A

classified of exposure and followed up over time

54
Q

what is the loss of follow up?

A

the person that leaves and loses all there data and can be called a bias data situation

54
Q

what are causes bias in cohort studies?

A

lose to follow up of people who may be related to the to the outcome of the study

55
Q

what is bias in RCT?

A

could be used if people who picked the people for this study and knew which group that the people would go into there exposure is assigned and not measured
lose of follow up can lead to bias in the experiment

56
Q

what is selection bias?

A

is the difference between who enters and who leaves the study

57
Q

what is the GATE study useful to see?

A

to see whats happening in a study when it comes to bias

58
Q

what is information bias?

A

collected by people who are involved with the study

59
Q

how does measurement error occur?

A

by participants providing inaccurate responses as they cant remember that clearly so could lead to being bias self reported information like this is called subjective

60
Q

what is a subjective measure?

A

pain

61
Q

what is objective measure?

A

using a peice of equipment like a faulty tool

62
Q

what is measurement error?

A

random lack of percision

63
Q

what is systematic error?

A

a lack of accuracy

64
Q

what can measurement error lead to in a descriptive study?

A

over/underestimation of prevalence

65
Q

what can measurement error lead to in analytic study?

A

misclassification which can be due to random or systematic error

66
Q

what can misclassification split into?

A

non-differential and differential

67
Q

what is non-differential misclassification?

A

when there is not different between the study groups
when the measurement error and any resulting misclassification occur equally in all groups being compared

68
Q

what is differential misclassification?

A

when there is different between the study groups

69
Q

which group does misclassification effect in thne outcome?

A

both groups

70
Q

what does misclassification do to the null value?

A

moves it closer to the null value

71
Q

how can recall bias occur in case control studies?

A

if they have to recall past exposures

72
Q

what is a recall bias?

A

systematic error due to the differences in accuracy or complteness of recall to memory of past events or experiences

73
Q

what does recall bias do to the OR?

A

incraeses the bias numerically upwards and the ratio value moves away from the null value

74
Q

how can we minimise recall bias?

A

we use iobjective measures instead of self-reported subjective measure

75
Q

what do we have to consider in cohort studies?

A

if they have been classified correctly

76
Q

what has already happened in historical studies?

A

the outcome

77
Q

what is the observer bias?

A

if the interveiwer knew the exposure of the group so they might ask more probing questions

78
Q

how do we minimise interveiwer/observer bias?

A

we clearly define study protocols and measures
structured questionaire and standard prompts
we can train the interveiwer or we can use blinding

79
Q

what can minimise RCT bias?

A

blindingh

80
Q

what are 3 ways on how we can minimise information bias?

A

collecting information from participants
measurement instruments
collecting information

81
Q

what do we do in collecting information from participants?

A

validating survey instruments
validate using objective measure such as looking at medical records

82
Q

what are measuerment instruments used for?

A

use standardised equipment, should be the same for all participants
use calibrated equipment, everything is working equally

83
Q

what is collecting information vai interveiws/observers?

A

blinding
use objective measures
use structured interviews and standard prompts
training of interviewers

84
Q

what is publication bias?

A

the publisher reports things that are not statistically significant or positive results

85
Q

what is confounding?

A

muddling the effects when the relationship we are interrested in is confused by the effect of something else

86
Q

what is the third factor that changes the risk outcome?

A

confounding

87
Q

what are the 3 properties of a potential confounder?

A

independently associated with the outcome
independently associated with the exposure
not on the casual pathway

88
Q

what is independantly associated with the outcome?

A

a risk/protective factor for the outcome by itself

89
Q

what is independently associated with the exposure?

A

different proportions of people with potential confounder across exposure groups

90
Q

what is ‘not on the casual pathway’?

A

not the mechanism by which the exposure affects the risk of the outcome

91
Q

what does confounding effect?

A

over-estimation of the true association, under-estimation of the true association,
change direction of the true association,
give appearance of a association when not one

92
Q

how do we identify the potential confounders?

A

we look for an imbalance between groups

93
Q

what are the 3 ways to control confounding?

A

randomisation
restriction
matching

94
Q

what does randomisation apply to?

A

anything we didnt know about and we dont have to know all the potential confounders in the study

95
Q

what is the only study that randomisation can be used on?

A

RCTs

96
Q

what is the only technique that can be used for known and unknoiwn confounders?

A

randomisation

97
Q

what does randomisation need?

A

equipoise and intention-to-treat

98
Q

what is restriction?

A

taking a particular confounder which is called a stratum

99
Q

what does restricting one confounder do?

A

we are able to make sure that they are alike.
can reduce generalisability and reduces the number of potential participants

100
Q

what does restriction have the potential for?

A

residual confounding with impercisly measured confounders and usually only one potential confounder

101
Q

what is matching?

A

when we choose people to make the control/comparison group have the same composition as the cases/exposed group reguarding the potential confounders

102
Q

what are matching used for?

A

in case-controlled studies

103
Q

what are the 2 groups that matching are split into?

A

individual and frequency

104
Q

what is individual matching?

A

each case mained with one or more controls having the same confounding visable characteristics

105
Q

what is frequency matching?

A

matching at the aggregated level

106
Q

what are the positives of matching?

A

useful for diffeercult to measure potential confounders and can improve effciency of case controlled studies with small numbers

107
Q

what are some negatives of matching?

A

individual matching can be differcult and limit potential numbers of potential participants
they also need special matched analysis for individual matching

108
Q

what are 3 ways that we can control confounding?

A

stratification,
multivariable analysis,
standardisation

109
Q

what is stratification?

A

calculating measure of association for each stratum of potnetial confounder and comparing them

110
Q

how do we stratificate?

A

first calculate the measure of association between exposure and outcome
we then divid the potential confounder into strata
for each stratum we calculate the measure of association between the exposure and outcome
we then compare stratum specific measures of association

111
Q

what are some pros of stratification?

A

easy for small numbers of potential confounders with limit strata
they can evaluate imopact of confounding and can identify effect modification

112
Q

what are some cons of stratification?

A

can leave residual confounding and can not be feasible when dealing with lots of potential confounders with many strata

113
Q

what is multivariable analysis?

A

statistical method for estimating measure of association whilst controlling for multiple potential confounders

114
Q

what are variety of different techniques are recognisable the term what?

A

regression

115
Q

what is standardisation?

A

used in measuring of disease occurance when we have 2 properties

116
Q

what are the limitations of standardisation?

A

have similar issues as stratification with multiple potential confounders of strata

117
Q

what are potential issues of controlling is study analysis?

A

result in residual confounding and can only control what youve measured

118
Q

why do we need to research ethics oversight?

A

to stop people from consenting to things that are unacceptably harmful

119
Q

what needs to be considered to research to be acceptable

A

-asses the benifits and harms and ensure the ratio is acceptable
-beaware of potential vulnerabilities of participants
-avoid or manage conflicts of intrest
-obtain informed consent from participants
-consider how the benefits and burdens of the research should be shared across society

120
Q

what is beneficience?

A

refers to the obligations that we have to benefit others

121
Q

what is non-maleficence?

A

refers to the obligations that we have not harmed others without a justifying reason

122
Q

what do research ethics committees require applicants to show?

A

-an awareness of the various costs or harms to participants includiong time, resources, coercive factors, and any oppotinity costs
-stratagies to address these harms and costs
-an awareness of potential culture sensitivities or intrests including the implications for maori
-evidence of the scientific validity of the research

123
Q

what is clinical equipoise?

A

the requirement that researchers only provide an experimental treatment if the evidence for the experimental treatment is equal to that available for the standard treatment

124
Q

what is a conflict of interest?

A

a situation where a person holds 2 or more potentially incompatible intrests
these are of concern in research where the researcher have intrests that might compromise the values and standards of ethically appropriate research

125
Q

what can arise conflict of intrests?

A

professionally, academically, financially, politically

126
Q

how can we manage conflicts of interest?

A

through peer reveiws
blinding
open access to data
auditing
independant people to recruit participants

127
Q

what is informed consent?

A

required when participants are enrolled in research studies

128
Q

what does informed consent require?

A

disclosure of the purpose
risks and process of the study
resonable efforts from the researcher to explain this information
the person is competant to give consent
absence of any coercive factors

129
Q

what must consent be in?

A

writing

130
Q

what does justice require?

A

transparency
that all people are considered of equal worth
that efforts are made to make the society equitable

131
Q

what does ACART mean?

A

advisory committee on assisted reproductive technologies

132
Q

what does ECART mean?

A

ethics committee on assisted reproductive technologies

133
Q

what are some enforcement processes?

A

prerequisite for finding public funding
prerequisite for publication in major health journals
clinical trial registry
professional obligation

Poph192 (4 decks)

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