Hoofdstuk 9: Quantitative research design deel 1

Question 1

Explain causality + citeria (6)

Answer 1

Treatment, prognosis and causation are concepts of causality (i.e. they are probablistic and not deterministic (100% of the time)).
Criteria:
-temporal (over time)
-relationship (effect related to cause)
-no confounding (no alternate explanations/variables)
-coherence
-consistency (we see consitence in appearance)
-biologival plausability

Question 2

What is the counterfactual model?

Answer 2

a counterfactual= what wouldve happened to the same people exposed to a causal factor is they were simultaniously werent exposed.

–> can be aproximated with experimental designs

Question 3

Explain the randomized control trial (RCT) (3 characteristics)

Answer 3

1. Manipulation: experimental (I) vs control condition (c) => observe effect in outcome
2. The control condition
3. Randomization: random allocation in (i) and (c)
   - basic/complete randomization
   - simple: prespecified in each group

Question 4

What are variants on randomizations in RCT ?

Answer 4

• stratified R (eg men and woman)
• permuted block
• urn R
• randomized consent: find participants –> randomise –> ask consent (! ethics)
• Partial R or partially randomized patient preference (participant wants random ? y:random n: choose (i) or (c)
• Cluster R (=groups as “participants”)

Question 5

What is blinding/masking ?

Answer 5

=concealing information about (study) from (everyone)

=> minimize expectation, performance and detection bias
e.g. singe-blind (participant) and double-blind (participant and researcher)

Question 6

Describe the conventional sequence of a RCT

Answer 6

1. Screen for eligibility (split)
2. Obtain informed consent (split)
3. Collect baseline date
4. Randomly assign (i) or (c) (split)
5. Administer intervention in groups
6. Collect outcome data

Question 7

Describe the basic experimental designs (2)

Answer 7

1. Multiple Intervention design:
   O1 –> R –> Xa –> O2
   O1 –> R –> XB –> O2
   O1 –> R ————> O2

2.Wait-list design
O1 –> R –> X –> O2 –> O3
O1 –> R –> O2 –> X –> O3

Question 8

Describe the factorial design

Answer 8

= manipulate 2 or more variables simultaniously (with random assignment to combinations) –> tests main effects and interaction effects

O1 –> R –> Xa1b1 –> O2
O1 –> R –> Xa1b2 –> O2
O1 –> R –> Xa2b1 –> O2
O1 –> R –> Xa2b2 –> O2

! large sample needed

Question 9

Describe the crossover design

Answer 9

=expose same individuals to all conditions (–> counter balance)

O1 –> R –> Xa –> O2 –> Xb –> O3
O1 –> R –> Xb –> O2 –> Xa –> O3

! washout period

Question 10

Describe some limitations of RCT

Answer 10

• Practical and ethical constraints
• Artificial setting
• Adherence to therapy
• Hawthorne effect (effect solely because someone participates in study)