Stimulus
Exp.
Posttest
Randomization Or matching
Control
Comparability
Compare
Compare
Pre-experimental vs. True Experimental Designs
Pre-experimental designs are designs that contain one or more features of true experimental design features, such a comparison group or random assignment.
Quasi-experimental Designs
1) Separate-sample pretest-posttest design
O1
X
R
X
O4
2) Nonequivalent control group designs
O1
X
O2
R
O3
O4
Quasi-experimental Designs (3)
Pretest
Stimulus
Exp.
Posttest
Randomization Or matching
Control
Comparability
Compare
Compare
Staging Experiments
Pretesting
Subject recruitment
Intro to experiment
Experimental Design
Experimental Design (Randomized Controlled)
Group Exper. Control
Байду номын сангаас
Random.
Re Rc
Obser.1 Treat Obser.2
Oe1
X
Oe2
Oc1
Oc2
Comparison
Oe2-Oe1 Oc2-Oc1
Manipulation of indep variable
Measurement of dep variable
Debriefing
Acquisition of informed consent
Random assignment
Manipulation check
Key Features of Experimental Approach
The New Design
1. Two groups: similar characteristics relevant to delinquency; one attend the program, another not.
2. Interview both groups about delinquent activity and family background before the program
Quasi-experimental designs lack some features of a true experimental design, “but permits stronger inferences about cause and effect than pre-experimental designs, by means of special design features and supplementary data.”
3. Interview all families 4. One year after the visit, interview both groups
about delinquent activity and changes in family 5. During step 4, also check arrest and conviction
Random Assignment vs. Random Sampling
Random sampling is a method of drawing a sample of cases, such as the pool of subjects in an experiment.
Random assignment is a method of assigning subjects from the pool to experimental conditions.
School type
Academic Achiv.
Child’s ability Parent resource
Home facility School type
School type Academic Achiv.
Academic Achiv.
Parent education value
Child valuation School type
研究设计实验研究的基本问题31
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研究设计:实验研究的基本问题
School of Public Administration & Policy Dr. Kaifeng Yang
问题
研究设计的核心要诣 实验设计的基本过程和环节 实验设计的影响因素
Given the research question, what type of evidence is needed to answer the question (or test the theory) in a convincing way?
1. Even without the program, no more than 30% would have been arrested
2. Family background: Volunteered are different 3. Committed crimes but not been caught 4. Only temporary effects 5. Participation labels them as potential criminals
Field experiments: studies that meet all the requirements of a “true” experiment but are conducted in a natural setting.
Experimental designs in survey research Unit of analysis other than individuals
3) Interrupted time-series design
O1 O2 O3 O4
X O5 O6 O7 O8
4) Multiple time-series design
O1 O2 O3 O4 O1 O2 O3 O4
X O5 O5
O6 O7 O8 O6 O7 O8
Experimentation Outside the Laboratory
Within subjects design: X1
O1
X2
O2
Each subject acts as his/her own control – that is, O1 is compared with O2 for
each subject.
Quasi-experimental Designs
Evidence of the versatility of experimentation comes from the incorporation of experimental design methodology into sample surveys and from the use of units of analysis other than individuals.
The quasi-experimental design falls into four subdivided categories, including 1) the separate-sample pretest posttest design, 2) Non-equivalent control group designs, 3) interrupted time-series design, and 4) multiple time-series design.
True experimental designs are those designs that meet the basic requirements for an experiment.
Pre-experimental Designs
Design 1: The One-Shot Case Study XO
Academic Achiv.
When you observe X and Y co-vary, the reason may be:
1x
y 2x
y
z
z
3x
y
z
4x
y 5x
y
z
z
6x
y
z
Coping with Rival Hypotheses
Operation Fright -- Juvenile Delinquency Visit prison…months ….70% not arrested
Design 2: The One-Group Pretest-Posttest Design
O1
X
O2
Design 3: The Static-Group Comparison
X
O1
O2