HSPH scientist Flashcards

1
Q

Bias in case control trials

A

Recall
Reverse causality
Selection of cases
Selection of controls

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2
Q

What is a nested case control study?

A

Cohort study

Then go back and do case control

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3
Q

Bias in cohort studies

A

Loss to follow up
Cohort selection
Exposure usually measured at just one point in time

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4
Q

Kaplan Meier curves

A

Plot survival over time

Can be used to generate Hazard ratios

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5
Q

Controls for RCTs

A

Geographical
Historical
Randomised

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6
Q

Parallel RCT

A

Only receive one treatment

For irreversible treatments

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7
Q

Crossover RCT

A
Receive both eventually 
Sequence randomised 
For reversible treatments 
Person acts as own control 
But takes longer
Carry over effects --> need washout period
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8
Q

Cluster RCT

A

Randomise pre-existing groups
E.g. schools, villages
Avoids contamination
Improves compliance

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9
Q

Factorial RCT

A

Tests >1 intervention

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10
Q

Sample power minimum

A

85%

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11
Q

Forest plot

A

Shows results of meta analysis

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12
Q

Problems with meta-analysis

A

Heterogeneity of data
- variation in results due to different methods, intervention
Publication bias
- data finding significant results favours publication
- inconclusive data less likely to be published

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13
Q

SD and % of data

A

1 SD = 68%

  1. 64 SDs = 90%
  2. 96 SDs = 96%
  3. 58 SDs = 99%
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14
Q

Two theories of ontology

A
Objectivism/realism = world is independent of us 
Subjectivism/contructivism = world is constructed by us
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15
Q

Two theories of epistemology

A
Positivism = things can be studies systematically like nature 
Interpretivism = humans are different so must be studied differently
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16
Q

Axiology

A

Study of value

17
Q

Deductive approach (positivist)

A

= testing a theory
Generate a theory
Collect data
Explain the relationship

18
Q

Inductive approach (interpretivist)

A

= generating a theory
Collect data
Analyse and generate theories

19
Q

Relative risk

A

Risk in treatment group

Risk in controls

20
Q

Number needed to treat

A

100

Absolute difference in risk

21
Q

Absolute difference in risk

A

For RCT
Risk in treatment - risk in controls

For cohort
Risk in exposed - risk in unexposed

For case-control
(population risk x odds ratio) - population risk

22
Q

Attributable population

A

p(relative risk -1)
1 + p(relative risk -1)

Where p = proportion exposed
In case controls, p = number exposed in controls
number of controls

23
Q

Odds ratio

A

odds of exposure in disease

odds of exposure on non-disease