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psy400ch9p216-
Experimental Independent Variables versus Participant Variables
| Term | Definition |
|---|---|
| independent variable | experimental condition that is systematically varied across participants |
| participant variable | characteristic that varies across participants but is not manipulated by the experimenters |
| main effect:The overall effect of a single factor | on the dependent variable, ignoring the effects of or averaging over the levels of all other factors. |
| Interaction: A situation,that arises when the effect of one factor (independent variable) | on the dependent variable is contingent on the levels of at least one other factor. |
| Interaction is the reason | for factorial methodology |
| An interaction refers to the joint effect | of multiple independent variables considered in combination, or in tandem |
| the effect of the factors that interact is more than a simple | cumulative effect of those factors (the interaction) |
| For example, a particular style of therapy might | work better for one type of client than for another. |
| Examining only main effects might miss | the important way in which factors operate jointly |
| Interaction chart | diagram that represents different combinations of the presence or absence of main and interaction effects. |
| Between-subjects Factorial Design Example | type of memory task and age/expertise, such that the memory task that evoked expertise (the chessboard) was enhanced more by the presence of expert knowledge |
| Within-subjects Factorial Design | involves conditions where the groups for each level of a factor are not independent of each other, but rather each group is exposed to each level of the factor |
| The term “repeated measures" reflects the idea that groups are | repeatedly exposed to the different levels of the factor(s) |
| Mixed factorial design (or mixed design) | A design that includes both within and between-subjects factors |
| Example of a Mixed Factorial Design (a 2 x 2) | After the pretest, randomly assign to one of two groups: the exposure or supportive psychotherapy. Finaly posttest. |
| Higher-order Factorial Designs | includes more than two independent variables. |
| Higher-order Factorial Designs: For example, a 2 x 2 x 2 design, | with three factors, two levels for each factor, and eight cells or conditions. |
| 2 (strategy) x 2(gender) x 3(age) design | one IV ( rote rehearsal or imagery) two participant variables, gender (male or female) and age (high school, college, middle age) |
| A higher-level factorial design is | best suited to capture the complexity of the world that we live in |
| Higher-order factorial designs may be used to | increase the external validity of your study. |