Chapter 4: Evidence about effects of intervention

Question 1

What are the forms of bias that commonly occur in uncontrolled studies?

Answer 1

• Volunteer bias
• Maturation
• Natural progression
• Regression to the mean
• Placebo effect
• Hawthorne effect
• Rosenthal effect

Question 2

What are uncontrolled studies?

Answer 2

Studies where the researchers describe what happens when participants are provided with an intervention, but the intervention is not compared with any others.

Question 3

What are some different types of participation randomisation designs?

Answer 3

• Simple randomisation
• Cluster randomisation
• Stratified randomisation
• Block randomisation

Question 4

What is intention-to-treat analysis?

Answer 4

Whether or not data from all participants were analysed in the groups to which participants were initially randomised, regardless of whether they ended up receiving the treatment.

Question 5

What does simple randomisation involve?

Answer 5

Involves randomisation of individuals to the experimental or the control condition.

Question 6

What does cluster randomisation involve?

Answer 6

Involves random allocation of intact clusters of individuals rather than individuals e.g. randomisation of schools, towns, clinics or general practices.

Question 7

What does stratified randomisation involve?

Answer 7

Participants are matched and randomly allocated to groups. This method ensures that potentially confounding factors such as age, gender or disease severity are balanced between groups.

Question 8

What does block randomisation involve?

Answer 8

Participants who are similar are grouped into ‘blocks’ and are then assigned to the experimental or control conditions within each block.