# Experimental Design Essay

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CHAPTER 8: EXPERIMENTAL DESIGN  The Experiment  Independent Variable-manipulated condition (CAUSE)  Counting Bones-Article #12  Unbussed table  Bussed table  Dependent variable-measure (EFFECT)  Counting Bones-Article #12  # of chicken pieces eaten  Weight of chicken CHAPTER 8: EXPERIMENTAL DESIGN  The Experiment Experimental control-variables are kept constant  Minimize confounds (variable varies along with IV)  Randomization   Counting Bones—Article #12 Experimental control  Separate dining room  Encouraged to help themselves……………..  Confounds…….? Question #9  Randomization  “tables were randomly assigned to conditions wherein either people’s plates would be regularly bussed or to a condition where people’s plates would not be bussed”  THE EXPERIMENT  Increase Internal Validity Experiment ability to determine causal relationships BASIC EXPERIMENT: BETWEEN SUBJECT DESIGN—INDEPENDENT GROUP DESIGN 2 LEVELS OF THE INDEPENDENT VARIABLE Random Assignment: Both groups are equivalent on participant characteristics (intelligence, age, etc.): Assigning SS to a condition is completely random; http://www.graphpad.com/quickcalcs/randomize2/ REPEATED MEASURE—WITHIN SUBJECT DESIGN Subjects receive each level of the independent variable  Participants are repeatedly measured  Same individuals participate in the two conditions  Read low meaningful material and take a recall test to measure learning Read high meaningful material and take a recall test to measure learning REPEATED MEASURE DESIGN  Advantages: Fewer subjects Conditions are identical because person is own control group Extremely sensitive to statistical differences More likely to detect effect of IV REPEATED MEASURE DESIGN  Disadvantages:  Order effect: the order of presenting the treatment affects the