Study Designs

Question 1

Randomized block design

Answer 1

• Randomised block: units from the sample are subdivided into ‘blocks’ based on pre-existing characteristics, then randomly assigned from blocks to a treatment

Question 2

Case control (observational)

Answer 2

Case control: subjects are selected based on a defined outcome, and a control group of subjects is selected separately to serve as a baseline with which the case group is compared

Ex., select cases of children who had pertussis and those who did not and compare them

Question 3

Cohort study (observational)

Answer 3

• Cohort studies: subjects sharing a common demographic characteristic are enrolled and observed at regular intervals over an extended period of time

Question 4

Sample survey (observational)

Answer 4

Sample survey: a random sample drawn from the entire population of interest at one point in time, and the sample is usually surveyed

Question 5

Completely randomized

Answer 5

• Completely randomised: units from the sample are each randomly assigned (randomised) to a treatment

Question 6

Matched pairs

Answer 6

• Matched pairs: pairs of units from the sample are matched based on similarity across pre-existing characteristics, then randomly assigned from pairs to treatments
• Can only have 2 treatments for this design
• Also includes repeat measures, as each individual is ‘matched’ with themselves when comparing data

Question 7

Control

• State the 4 types of control

Answer 7

• Control: account for variation in ‘other’ variables to isolate effects of the explanatory variable(s) of interest
  
  1. Limit variation
  2. Blocking
  3. Blinding
  4. Comparison