PSYC 2250 Lecture Notes - Lecture 11: Interrupted Time Series, Causal Inference, Internal Validity
26 Jun 2018
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PSYC 2250 Introduction to Psychological Research
Chapter 11 Single Case, Quasi-Experimental, and Developmental Research
Single Case Experimental Designs
Single case experimental design: often seen in clinical, counselling, educational, and other
applied settings
- Were developed from a need to determine whether an experimental manipulation has an
effect on a single research participant
- Subject’s behavior is measured over time during a baseline control period.
- Then treatment is introduced subjects continue to be observed
- A change in the subject’s behavior from baseline to treatment period is evidence for the
effectiveness of the manipulation; but it might leaded by any other variable.
Reversal Designs
A (baseline period) B (treatment period) A (baseline period)
To prove the independent variable affect the dependent variable show it could be undone
As ABA design is not extremely powerful evidence for the effectiveness of the treatment
extend to ABAB design, even ABABAB….
Multiple Baseline Designs
Some behavior might be impossible or unethical to reversed, e.g. alcoholism, compulsive theft…
In multiple baseline design, the effectiveness of the treatment is demonstrate when a behavior
changes only after the manipulation is introduced
- Observed under multiple circumstances to rule out the possibility that other events were
responsible
3 variations: across subject; across behavior, and across situation
A) Across subject: the behavior of several subjects is measured over time; for each subject, the
manipulation is introduced at a different point of time
E.g. smoking reduction
B) Across behavior: several different behaviors of a single subject are measured over time;
same manipulation applied to each of the behavior at different times
Reward system
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PSYC 2250 Introduction to Psychological Research
C) Across situation: the same behavior is measured in different settings; the manipulated is
introduced at different time
Program Evaluation
Program evaluation: research on programs that are proposed and implemented to achieve
some positive effect on a group of individuals
5 types of questions
1. Needs assessment: asks problems that need to be addressed in a target population
Are there problem that need to be addressed in a target population?
2. Program theory assessment: ask question to get information to make sure program based
on valid assumption
How will the problems be addressed? Will the proposed program actually address
the needs appropriately?
3. Process evaluation: to determine whether it is reaching the population, whether it is
attracting enough clients…
Is the program addressing the needs appropriately?
4. Outcome evaluation: evaluate the goal
Are the intended outcomes of the program being realized?
5. Efficiency assessment: does it worth?
Is the cost of the program worth the outcomes?
Quasi-Experimental Designs
Quasi-experimental designs: address the need to study the effect of an independent variable in
settings in which the control of true experimental designs cannot be achieved
- Less causal inference, lower internal validity
- So used only when true experiments are impossible to conduct
A) One-Group Posttest-Only Design
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Document Summary
Chapter 11 single case, quasi-experimental, and developmental research. Single case experimental design: often seen in clinical, counselling, educational, and other applied settings. Were developed from a need to determine whether an experimental manipulation has an effect on a single research participant. Subject"s behavior is measured over time during a baseline control period. Then treatment is introduced subjects continue to be observed. A change in the subject"s behavior from baseline to treatment period is evidence for the effectiveness of the manipulation; but it might leaded by any other variable. A (baseline period) b (treatment period) a (baseline period) To prove the independent variable affect the dependent variable show it could be undone. As aba design is not extremely powerful evidence for the effectiveness of the treatment extend to abab design, even ababab . Some behavior might be impossible or unethical to reversed, e. g. alcoholism, compulsive theft .
