Experimental Designs

Question 1

What is non-experimental research?

Answer 1

• researcher observes the phenomena as they occur naturally; doesn’t intervene
• descriptive research
• correlational research

Question 2

What is experimental research?

Answer 2

• researcher plays an active role by manipulating the IV
• examines cause and effect
• randomised controlled trial

Question 3

What are the 2 types of design?

Answer 3

Experimental and correlational
- both designs start with an experimental hypothesis that predicts a relationship between 2 variables but the aims and methods of each approach are different

Question 4

What are the different levels of the hierarchy of evidence?

Answer 4

1. Systematic review
2. Randomised control trail
3. Cohort studies
4. Case reports
5. Expert opinion

Question 5

What are the different significance of evidence levels?

Answer 5

1. Randomised controlled studies
2. Controlled longitudinal studies
3. Uncontrolled longitudinal studies
4. Cross-sectional studies and case studies
5. Expert opinions

Question 6

What are the different elements of study design?

Answer 6

• objectivity
• hypothesis testing
• experimental and study designs
• large representative samples
• data collection by structured instruments
• numerical data
• analysis by statistical tests
• conclusion bass on statements of probability
• validity and reliability
• generalisability

Question 7

What are cohort studies?

Answer 7

• looking for differences between groups and try to identify variables
• looking for a causal relationship

Question 8

What is required to infer causality?

Answer 8

• the cause must precede the effect
• the causal variable and effect variable must be associated with each other
• the relationship must not be explicable by any other cause

Question 9

What do experimental designs include?

Answer 9

• manipulation
• control
• randomisation

Question 10

What do quasi-experimental designs include?

Answer 10

• similar to experimental designs
• less control (no comparison group, not randomised)
• less certain that results are due to the intervention

Question 11

What is manipulation?

Answer 11

• process by which the researcher manipulated the IV in order to determine the effect on the DV

Question 12

What are RCTs?

Answer 12

• highest level of evidence
• reduced bias
• ran done allocation of pts to intervene group or control/usual care group
• use CONSORT guidelines

Question 13

What is the consort statement?

Answer 13

• consolidates standards of reporting trials
• 25 item checklist for elements of RCT
• flow chart of participant progress

Question 14

What is a control group?

Answer 14

• group of participants whose performance on the DV is used to evaluate the performance of the experimental group on the same DV
• without a control group it is not possible to know if changes in the DV are due to the IV

Question 15

How do you reduce the possibility of extraneous factors having an impact on the outcome?

Answer 15

• manipulation of the IV
• comparison/control group
• randomisation

Question 16

What does randomisation ensure?

Answer 16

• group assignment is independent of participant characteristics
• every person in a target population should have equal chance of being selected
• every selected person should have equal chance of assignment to experiment or control group

Question 17

What are the different types of randomisation?

Answer 17

• simple
• block
• stratified

Question 18

What is simple randomisation?

Answer 18

Computer generated random numbers

Question 19

What is block randomisation?

Answer 19

Ensures that the numbers of participant assigned to each group is equally distributed; commonly used in smaller trails

Question 20

What is stratified randomisation?

Answer 20

Ensures that important baseline variables (potential confounding factors) are evenly distributed between groups

Question 21

What are the elements of randomisation before an assignment?

Answer 21

• sequence generation

- allocation concealment

Question 22

What are the elements of randomisation after an assignment?

Answer 22

Blinding

Question 23

What is sequence generation?

Answer 23

Rule for allocating interventions should be based on chance

Question 24

What are adequate methods of sequence generation?

Answer 24

• dice
• shuffled cards
• random numbers

Question 25

What are inadequate methods of sequence generation?

Answer 25

Systematic (predictable) methods e.g. Date of birth

Question 26

What is allocation concealment?

Answer 26

- works in conjunction with sequence generation | - shields those enrolling participants from knowing upcoming assignments

Question 27

What are adequate methods for allocation concealment?

Answer 27

- numbered - opaque - sealed envelopes - sequentially numbered drug containers - central randomisation

Question 28

What is blinding?

Answer 28

- could participants/study personnel have knowledge of group assignment, if so, could the knowledge affect the outcomes?

Question 29

What is the role of the p-value when testing a hypothesis?

Answer 29

Reports the the probability of obtaining a study result of the null hypothesis is true

Question 30

What does a small p-value indicate?

Answer 30

- results are unlikely when the null hypothesis is true - null hypothesis is rejected (

Question 31

What does a large p-value indicate?

Answer 31

- results obtained are likely when the null hypothesis is true - null hypothesis is accepted (>0.05)

Question 32

What is type 1 error?

Answer 32

Finding a significant difference when it doesn't exist and rejecting the null hypothesis

Question 33

What is type 2 error?

Answer 33

Failure to find a significant difference when there really is one and accepting the null hypothesis

Question 34

What are the characteristics of true/classical experiments?

Answer 34

- randomisation - manipulation - control

Question 35

What are the constraints of a true experiment?

Answer 35

- in a real life setting, controls are difficult to apply - individual nature of human subjects - expensive - difficulties with randomisation

Question 36

What are the different sources of bias?

Answer 36

- selection bias - performance bias - attrition bias - measurement bias - Hawthorne bias

Question 37

How do you minimise selection bias?

Answer 37

Random assignment to groups

Question 38

How do minimise performance bias?

Answer 38

Mask/blind interventions if possible and clearly defined protocols

Question 39

How do minimise attrition bias?

Answer 39

Follow up all who leave the study and faithful reporting of attrition

Question 40

How do you minimise measurement bias?

Answer 40

- reliable, valid measurement tools/instruments and trained testers/data collectors

Question 41

How do you minimise the Hawthrone effect?

Answer 41

Compare control and experimental interventions

Question 42

What are the difficulties with experimental designs?

Answer 42

- manipulation of IV or randomisation may not be feasible/ethical - DV may not be measurable - long term or rare outcomes or those unkown to be important at start of trial

Question 43

What are the elements of a research question?

Answer 43

- PICO - patients/population/problem - intervention - comparison - outcome