241109 rm-p.l.-experimental design
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EXPERIMENTAL DESIGN DR. PREMILA LEE, Professor, Dept of Surgical Nursing & CNE & Research, College of Nursing, Christian Medical College, Vellore
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Transcript of 241109 rm-p.l.-experimental design
EXPERIMENTAL DESIGN
DR. PREMILA LEE,Professor,
Dept of Surgical Nursing & CNE & Research,
College of Nursing,Christian Medical College,
Vellore
INTRODUCTION
• Purpose of scientific research is to determine cause & effect relationship
• To determine the efficacy of an intervention
• Researcher – active
• Provides for evidence based practice
Is there an intervention?
No
Non experimental research
yes
Is there random assignment to treatment groups?
Yes
Experimental
research
Are there measures to compensate for lack of random assignment
No
No Yes
Quasi experimentalPre experimental
TYPES
• True experimental
• Quasi experimental
CHARACTERISTICS
• Manipulation
• Control
• Randomization
MANIPULATION
• Researcher gives intervention or treatment
• Manipulates the independent variables
• Observe the effect
CONTROL
• Used as a basis of comparison
• Possibilities for the counterfactual
- Alternative intervention
- Placebo effect
- Standard care
- Wait list control group
RANDOMIZATION
• Random assignment
• Every subject has an equal chance
• Cluster randomization
• Advantages - No systematic bias - Allows comparison - Increases confidence
EXPERIMENTAL DESIGN
• Pre test - Post test control group design
• Solomon four group design
• Factorial design
• Randomized block
• Cross over design
PRETEST POSTTEST DESIGN
R
E
C
Pre test X Post test
Pre test Post test
SOLOMON FOUR GROUP DESIGN
R
E2
Pre test X Post test
X Post test
C1 Pre testPost test
E1
C2 Post test
FACTORIAL DESIGN
Type of stimulation
Daily exposure
Auditory
A1
Tactile
A2
15 minutes
B1
A1 B1 A2 B2
30 minutes
B2
A1 B2 A2 B2
45 minutes
B3
A1 B3 A2 B3
RANDOMIZED BLOCK DESIGN
• Similar to factorial design in structure
• Two independent variable (factor) - one is not manipulated – known as blocking variable
• Can include more than one blocking variable
CROSS OVER DESIGN
• Repeated measures design
• Within subject design
• Subjects as their own control
• Equivalence among subjects
STRENGTHS
• Powerful to test hypothesis
• Yields highest quality of evidence
• Provides greater confidence
LIMITATIONS
• Impractical or impossible at all times
• Artificiality
• Difficulty in clinical setting
• Hawthorne effect
• Ethical concern
• Costly
QUASI EXPERIMENTAL
• Non equivalent control group before and after design
• Time series design
NON EQUIVALENT CONTROL GROUP BEFORE AND AFTER DESIGN
O1 X O2
O1 O2
E
C
LIMITATIONS
• Lack of randomization
• Control group is not equivalent
TIME SERIES DESIGN
O1 O3O2 O4 X O5 O6 O7 O8
Time series non equivalent control group design
O1 O3O2 O4 X O5 O6 O7 O8
O1 O3O2 O4 O5 O6 O7 O8
PRE EXPERIMENTAL
• One group pre test post test design
• One group posttest- only design
• Non equivalent control group after only design
One group pretest post test design
O1 X O2
ONE GROUP POSTTEST ONLY DESIGN
X O2
POSTTEST ONLY DESIGN WITH COMPARISON GROUP
R
E
Non equivalent comparison group
X Post test
Post test
QUASI EXPERIMENTAL - STRENGTHS
• Practical & feasible
• Adaptable to real world
• Some studies it is the only way
QUASI EXPERIMENTAL - STRENGTHS
• Cause & effect influences less convincing
• Not objective
• Experiment & comparison groups are not equal
CONCLUSION
• To meet the growing demand for evidence based practice
