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RESS > RESS Notes > Flashcards

RESS Notes Flashcards

1
Q

Representative sampling

A

Choosing a sample representative of whole population

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2
Q

Exposure

A

Something participants are exposed to, an attribute or a behaviour

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3
Q

Outcome

A

Result being investigated

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4
Q

Variable

A

Characteristic that differs between individuals and can be measured

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5
Q

Dependant variable

A

variable that changes based on changes to another variable

ie the outcome

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6
Q

Independent variable

A

variable that causes changes in other variables

ie the exposure

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7
Q

Proxy variable

A

not normally of interest but has close correlation to variable of interest

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8
Q

Confounding variable

A

interferes with relationship between dependent and independent variable (causes outcome and exposure)

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9
Q

Mediator

A

State that occurs between exposure and outcome - no effect on outcome
Do not adjust for mediators

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10
Q

Competing exposure

A

Different exposure that causes same outcome

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11
Q

Nominal data

A

Categorical eg marital status

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12
Q

Ordinal data

A

Categorical in order ie good, very good, excellent

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13
Q

Discrete data

A

Quantitative, whole numbers

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14
Q

Continuous data

A

Quantitative, on a continuum

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15
Q

Data collection proforma

A

Questionnaire to ensure variable are consistently and accurately measured

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16
Q

Linear modelling

A

Indicates if there is an association between 2 variabls

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17
Q

Confidence intervals

A

Range of values within which researches are confident that the results of repetition of the study would fall
When applied to odds ratios, if CI includes 1 then conclusion is that exposure is not related to outcome

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18
Q

Confidence level

A

probability that repeated results will fall within confidence intervals

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19
Q

Number needed to treat

A

Average number of patients who need to be treated to prevent one additional bad outcome
Ideal = 1
Lower the better

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20
Q

Number needed to harm

A

average number of patients who need to receive treatment in order for one bad outcome to occur

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21
Q

Absolute risk

A

Difference between control group’s event rate and experimental group’s event rate

22
Q

Relative risk

A

AKA risk ratio

ratio of probability of an event occurring in exposed group to the probability in the non exposed group

23
Q

Odds ratio

A

Used to quantify how closely linked an exposure and an outcome are

>1 = association more likely in control group
1 = no difference to control group
<1 = association less likely in control group
24
Q

Adjusted odds ratio

A

Odds ratio after adjusting for confounding variables and competing exposures

25
Q

P value

A

Probability of obtaining a result as extreme as the one observed, given the null hypothesis is true
P <0.05 = statistically significant
P >0.05 = not significant

26
Q

Randomised control trials

A

Participants are randomly allocated to receive treatment or not
Can be double blind, single blind or non blind

27
Q

What observational studies are there?

A

Cohort
Cross sectional
Case control
Ecological

28
Q

Cohort study

A

Analysis of risk factors, follows cohort of people without disease who share characteristic over period of time
Can be prospective - will control all testing but can lose patients in follow up
Can be retrospective - immediately available data but can only examine prognostic factors
Can be time series - repeated observation of the same variables in the a cohort at designated points in time

29
Q

Cross sectional

A

Collect data from population at particular point in time
Descriptive studies
Used to describe odds ratios, absolute risks and relative risks
Useful to analyse prevalence

30
Q

Ecological study

A

Studies of risk-modifying factors on health defined geographically or temporally

31
Q

Case control study

A

Two groups with different outcomes are compared on the basis of a causal attribute

32
Q

Meta analysis

A

Contrast and combine results of multiple studies to identify patterns
Difficulties: differences in data collection + differing criteria
Requires careful data extraction, manipulation and assessment

33
Q

Aetiological studies

A

Provide info on risk factor and causes of a condition

Can only prove correlation

34
Q

Diagnostic studies

A

Shows specificity and sensitivity of a diagnostic test

35
Q

Prognostic studies

A

Provide info on outcome and morbidities of patients after exposure

36
Q

Therapeutic studies

A

Provide info on effectiveness of treatment

37
Q

Pros and cons of prospective data collection

A

Follows patients who share a characteristic
Pros: less missing data, reliable info
Cons: time consuming, large amount of data to analyse

38
Q

Pros and cons of retrospective data collection

A

Pros: immediately available data
Cons: no control of variables, often missing data

39
Q

How can you identify confounding variables?

A

Draw a directed acyclic graph to show causative relationships

40
Q

Describe linear modelling

A 
Uses parsimony (prefers the simplest explanation)
Mean part = the relationship
Residual part = unexplained and error (normally distributed)
Have to adjust results to account for effects of confounding variables and competing exposures
41
Q

PECOS

A 
Patient
Exposure
Comparison
Outcome
Study design
42
Q

Controlled vocab search

A

Medline uses MeSH - medical subject headings

43
Q

Principles of critical appraisal

A 
Is research:
Relevant 
Robust 
Objective 
Important
44
Q

How is research robust?

A

Good design, no bias:
Sampling bias - random sampling, multi site
Measurement bias - info bias, observer bias, recall bias?
Analytical bias - loss to follow up, omitted variables?
Dissemination bias - publication bias?

45
Q

How is research important?

A

If there is good quality of design (no of patients) and good strength of evidence

46
Q

What is required for effectiveness of evidence?

A 
Controlled trials 
Randomisation 
Concealment and masking 
Low drop out and intention-to-treat 
Sufficient statistical power
47
Q

Describe a critical appraisal of a prognostic study

A

Routinely collected
Bespoke measurements
Ignore studies with >80% LTFU (lost to follow up)
Compare baseline data of LTFU with non LTFU
Conduct sensitivity analysis

48
Q

Describe a critical appraisal of a diagnostic study

A

What is sensitivity and specificity of test? What is predictive value of positive and negative test result?

49
Q

Sensitivity

A

Ability of test to pick up true positives

50
Q

Specificity

A

Ability of test to avoid false positives

51
Q

What is external validity?

A

Appropriate spectrum of patients - participants must have same range of severity, symptoms and prevalence of condition as target population

52
Q

What are the key issues with evidence from an aetiological study?

A

External validity of participants
Exposures/ outcomes measured blind
Follow up - was sufficient time left for outcome to occur?
Loss to follow up - assess potential differential bias

RESS (11 decks)

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