Chapter 7

Question 1

observational research

Answer 1

naturally occurring variation observed to identify patterns and associations
natural history od disease

Question 2

type of observational study

Answer 2

case series 
ecological
surveys and cross sectional 
case control 
cohort 
qualitative

Question 3

experimental research

Answer 3

investigator controls 1 factor and measures variation in outcome
clinical trials
impact of preventative vaccines or behaviour change programs

Question 4

type of experimental research

Answer 4

RCT
cluster RCT
cross over trials
factorial trials

Question 5

modelling and stimulation research

Answer 5

development of theories
validity dependant on data used to set up model parameters
study disease transmission and empirical data

Question 6

hierarchy of evidence

Answer 6

Systematic review and meta-analysis of trials.
• RCTs.
• Cohort studies.
• Case–control studies.
• Ecological studies.
• Cross-sectional studies.
• Case reports and case series.
• Expert opinion.

Question 7

exposure

Answer 7

describe something that might affect an outcome
explanatory or independent variables
exposure of interest -= one in the hypothesis

Question 8

outcome

Answer 8

response or dependant variables

can have more than 1 outcome per study

Question 9

confoiunder

Answer 9

independantkly associated with the exposure and outcome of the study
can lead to bias
explanatory or independent variables

Question 10

bias

Answer 10

deviation from the truth that occurs in studies

systematic error is different from random error - increasing the sample size can reduce random error but not bias

Question 11

selection bias

Answer 11

recruit participants based on characteristic linked to exposure and outcome
occurs in allocation to intervention
non-responders different to responders - healthy participant effect

Question 12

measurement bias

Answer 12

systematic errors in measurement including errors in allocation to different groups
systematically wrong - recall bias in case control

Question 13

association

Answer 13

statistical dependence between 2 variables - indicates the degress to which the outcome is different in those with(out) exposure

Question 14

chance

Answer 14

inference from samples
repeat in different sample and results would be different
use CI to determine likelihood of chance being a factor

Question 15

observer bias

Answer 15

RCT

researxher aware of the treatment that the person is getting

Question 16

information bias

Answer 16

difference in the way that the information is collected and so different qualities between groups of the study

Question 17

non-differential misclassification

Answer 17

chance of misclassification is the same regardless of the disease status/exposure
random misclassification
bias association towards null - masks true differences

Question 18

differential misclassification

Answer 18

probability of exposure being misclassified depends on the disease status/vice versa
can bias estimates in either direction

Question 19

confounding

Answer 19

false association because it distorts the observed association

Question 20

randomisation

Answer 20

adjust for confounding at the design stage

distribution of confounding factors should be the same in both groups

Question 21

matching

Answer 21

case control

select cases and controls so match on confounding factors

Question 22

adjusting for confounding at analysis stage

Answer 22

stratification
standardisation
multiple regression

Question 23

association/causation

Answer 23

exclude chance bias and confounding = true association - doesn’t necessarily mean causal

Question 24

Bradford hill criteria

Answer 24

strength of association
consistency of association 
specificity of association 
temporal sequence of association 
dose response relationship 
biological plausibility of association 
coherence 
reversibility 
analogy

Question 25

strength

Answer 25

measured by RR

stronger = more likely causal

Question 26

consistency

Answer 26

repeated demonstration in different populations and study designs

Question 27

specificity

Answer 27

1:1 relationship between cause and outcome

Question 28

temporal

Answer 28

risk factor before outcome

Question 29

dose response

Answer 29

gradient of risk

Question 30

plausibility

Answer 30

known biological mechanism

Question 31

coherence

Answer 31

absence of conflict with other knowledge about the natural history and disease

Question 32

reversibility

Answer 32

remove the risk factor prevent the outcome

Question 33

analogy

Answer 33

analogy with other similar causal associations

Question 34

causality and public health

Answer 34

absolute proof rarely attainable in empirical sciences

Question 35

how important are causal relationships

Answer 35

knowledge of causal mechanism not essential for effective preventative strategies