Study Designs

Question 1

Ecological

Answer 1

Population-level data
eg electoral role

Question 2

Ecological advantages

Answer 2

Fast
Inexpensive
Few ethical issues
Data collection fairly easy
Can look at trends between regions or over time

Question 3

Ecological Disadvantages

Answer 3

Cannot determine individual-level associations
Cannot demonstrate cause and effect
Lack of control over variables collected

Question 4

Cross-sectional

Answer 4

Outcome and exposure status measure simultaneously

Question 5

Cross-sectional advantages

Answer 5

Can look at associations- hypothesis generating
Data collection fairly easy
Can study multiple exposures and outcomes
Fast
Inexpensive

Question 6

Cross-sectional disadvantages

Answer 6

Cannot demonstrate cause and effect
Prone to bias and confounding
Not useful for rare exposures or outcomes

Question 7

Case-control

Answer 7

Participants selected on the basis of outcome

Question 8

Case-control advantages

Answer 8

• Can look at association between outcome and prior exposures
• Fast
• Inexpensive
• Good for studying rare outcomes
• Can study multiple exposures

Question 9

Case-control disadvantages

Answer 9

• Cannot determine incidence/risk of outcome
• Limited control over data quality – poor historic records or recall bias
• Retrospective nature limits ability to determine causality
• Not useful for rare exposures

Question 10

Cohort

Answer 10

Participants selected in the basis of exposure

Question 11

Cohort advantages

Answer 11

• Can look at incident cases and associations with exposure
• Good for studying rare exposures
• Can study multiple outcomes
• Control over data collected
• Exposure determined before outcome occurs so can demonstrate temporality for potential cause and effect

Question 12

Cohort disadvantages

Answer 12

• Mostly prospective which can be time consuming
• Risk of loss to follow-up
• Expensive
• Not useful for rare outcomes

Question 13

Randomised controlled trial

Answer 13

Participants randomly allocated to interventions then followed up to compare outcomes
Experimental study with random allocation into treatment groups (NOT random sampling)

Question 14

RCT advantages

Answer 14

• Can study intervention effects on outcome(s)
• Random allocation means confounding factors should be evenly distributed
• Control over variables collected
• Comparator group means ability to account for placebo/temporal effects
• Less prone to bias, particularly where blinding and objective outcome assessment used
• Gold standard for establishing causality- can show cause-effect relationship

Question 15

RCT disadvantages

Answer 15

• Time consuming
• Expensive
• Require expertise to run
• Can only be used where ethics and participant willingness permit randomisation to intervention
• Overly strict eligibility criteria may render sample not fully representative of population
Affected by non-compliance
Not practical for long-term effects

Question 16

Case control studies can only use…

Answer 16

Odds not risks

Question 17

Three-arm trial

Answer 17

a 3-arm trial consists of the intervention, the active control, and a placebo arm. This design is particularly attractive when the efficacy of the active control has changed, is volatile, or is in doubt

Question 18

Cluster randomisation

Answer 18

a randomised controlled trial in which pre-existing groups, called clusters, of individuals are randomly allocated to treatment arms. For example, clusters may be clinical practices or schools where the individuals are patients and school children, respectively.

Question 19

2 characteristics a placebo treatment should have

Answer 19

1. Inactive form of ingredients
2. Identical look and administration of treatment

Question 20

Blinded

Answer 20

Participants do not know whether they receive treatment or placebo

Question 21

Random assignment

Answer 21

Assignment is unpredictable and equal probability of ending up in either group

Question 22

Hierarchy of evidence

Answer 22

1. Systematic review of RCTs
2. RCT
3. Cohort
4. Case control
5. Cross-sectional
6. Case series
7. Anecdote

Question 23

2 types of observational study

Answer 23

Descriptive and analytical

Question 24

Descriptive study : individuals

Answer 24

Case report
Case series

Question 25

Descriptive study : populations

Answer 25

Ecological study
Cross-sectional study

Question 26

Single time point analytical study

Answer 26

Cross-sectional study- population: see how many have disease and how many have symptoms
Exposure <-> outcome

Question 27

Retrospective analytical study

Answer 27

Case-control study- compare prevalence of symptoms in control vs disease group
Outcome —> exposure

Question 28

Prospective analytical study

Answer 28

Cohort study- sample of unaffected and measure exposure to risk factor over time
Exposure —> outcome

Question 29

Experimental intervention study

Answer 29

Randomised controlled trial

Question 30

Types of RCT

Answer 30

Cluster
Crossover
Multi-arm + factorial
Adaptive

Question 31

Cluster RCT

Answer 31

Randomise groups rather than individuals

Question 32

Crossover RCT

Answer 32

Receive both interventions in randomised order
ONLY if incurable or chronic

Question 33

Multi-arm + factorial RCT

Answer 33

> 1 interventions compared

Question 34

Adaptive RCT

Answer 34

Accruing information informs study eg early termination I’d clear treatment difference