Independent group design

What is independent group design?

1. 5 4 3 2 1 : 4 3 2 1

2. Independent group design Shayan Iqbal

3. Matched Group Design Independent Group Design Random Group Design Natural group design

4. Important Concepts Related To Experimental Research Why psychologists conduct experiments ? Researcher conduct experiment to test the hypothesis about causes and behavior. Experiments allow researcher to decide whether a treatment or program effectively change behavior. Random Group Design When random assignment to treatment conditions is used, the independent group design is called a random group design.

5. Important Concepts Related To Experimental Research Random Assignment Experiments in which each separate group of subject in the experiment represent a different conditions as defined by level of IV. It uses random assignment of subject to conditions in order to prior to implementing the IV. Rationale of Independent group design Can conduct the experiment to study treatment effect. Ability to make between group comparison. Use of control group to infer change in experimental group only due to treatment. Threats to internal validity Occurrence of event between treatment condition and measurement effect. Time span between treatment conditions and measurement effects. Presence of plausible alternative.

6. Logic of experimental research Experimental manipulation Researcher manipulate an IV in an experiment to observe the effect on behavior, as assessed by the dependent variable. Experimental control Experimental control allow researcher to make causal inference that the IV cause the effect change in DV. Manipulation, holding condition constant, balancing. Internal validity The IV caused the difference in behavior as measured by the DV. Three conditions required for causal inferences; covariation, time order relationship, elimination of plausible alternative causes.

7. High internal validity of experiment Covariation When to different measures of the same people , event vary to together- that is when scores on one variable covary with scores on other variable. Time order relationship The efforts to maintain minimum possible time between treatments and measurement effects. Elimination of plausible alternative causes When confounding occur plausible alternative explanation for the observed covariation exists, the experiment lacks internal validity. Holding condition constant and balancing.

8. Elimination of plausible alternative causes Holding condition constant It is to make sure that the IV is the only factor that differs systematically across the group. Balancing Balancing the difference among subject tested from heterogenous population. Forming comparable groups at the start of experiment. Averaging As a part of balancing the researcher averages the individual differences among subject across the group of the experiment .

9. Elimination of plausible alternative Objective Dittmar et al.(2006). There goal was to determine whether exposure to very thin body images causes young girls experience negative experience about their own body. Sample In the experiment small group of young girls read a story about Mira as she went shopping for clothes and prepared to go to the birthday party. Procedure as they heard the story, the girls looked at the pictures with six scenes related to story.

10. Treatment conditions Condition 1 Condition 2 Condition 3

11. Conditions of experimental design IV and DV Manipulation of IV Cause effect b/w IV and DV IV: Exposure to Body Image DV: Dissatisfaction IV: Exposure to Body Image C1 C2 C3 X1 X2 X3 IV: Exposure to Body Image Barbi Eme NU O3 O2 O1

12. Random Assignment to treatment conditions and observation of behavior Stage 1 : Random Assignment Stage 2: Random assignment to treatment condition Stage 3: Observation of behavior Girls R1 R2 R3 X1 X2 X3 Barbi Eme NU O3 O2 O1 R1 n=17 R2 n=20 R3 n=20 R1 R2 R3

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