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Experimental Design

Experimental Design. Research Methods. Independent variable (treatment) . The independent variable is manipulated by the experimenter. Examples of independent variables include: Fitness levels, type of practice, contextual interference, strategy for imagery, music … Controls

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Experimental Design

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  1. Experimental Design Research Methods

  2. Independent variable (treatment) • The independent variable is manipulated by the experimenter. • Examples of independent variables include: Fitness levels, type of practice, contextual interference, strategy for imagery, music … • Controls • Active and assigned variables • Between subjects and within subjects (repeated measure) variables

  3. Within Subjects/Repeated Measure Counterbalancing, using a Latin Square Design When an experiment has multiple treatments, conditions, or tasks they can be counterbalanced across subjects by using a Latin Square Design. In using a Latin Square Design all orders are not represented; however , all conditions are represented at least once in each position of the order to observe the effects of position and to control for practice, boredom, fatigue….

  4. Dependent Variable • The dependent variable is the variable measured by the experimenter (e.g., reaction time, heart rate, VO2Max, a survey score) • Concerns • Standardization • Validity • Reliability • Objectivity • Sensitivity

  5. Statistical Testing • Categorical Independent Variables; Continuous Dependent Variables • Differences • T-test • ANOVA • Categorical Independent Variables; Categorical Dependent Variables • Associations • Chi squared • Continuous Independent Variables; Continuous Dependent Variables • Relationships • Correlation • Regression

  6. Writing Hypotheses • Null • Directional • Alternative

  7. Null Hypotheses • State the null hypothesis when no literature exists • State the null hypothesis when the literature is controversial or equivocal • State when there is no theoretical direction

  8. Writing Null Hypotheses • Stated in the null form • Independent variable (insert name) will not affect dependent variable (insert name). • Independent variable (insert name) will not associate with the dependent variable (insert name). • Independent variable (insert name) will not relate to the dependent variable (insert name).

  9. Directional Hypothesis • State when the literature provides a clear direction • State when the literature is unequivocal • State when good theoretical support exists

  10. Writing Directional Hypotheses • Independent variable (levels A and B) will affect the dependent variable such that A will be significantly different than B. • Independent variable (levels A and B) will associate with the dependent variable such that B will be significantly associated with B in specific ways. • Independent variable (levels A and B) will relate to the dependent variable such that B will be significantly and positively (or negatively) related to B.

  11. Writing Problems • How does the independent variable affect the dependent variable? • How does the independent variable associate with the dependent variable? • How does the independent variable relate to the dependent variable?

  12. Main Effects and Interaction effects • Also you might need to consider interaction and main effects? What if you have two independent variables? • Main effects include the analysis of a single independent variable and all of its levels. • Interaction effects include the analysis of more than one independent variables and the interaction of all of their levels.

  13. Interaction of Two Independent Variables (3*2 factorial design)

  14. Pure Experimental Designs • Randomized groups Design • Pretest-Posttest Randomized-Groups Design • Solomon Four-Group Design

  15. Randomized-Groups Design

  16. Pretest-Posttest Randomized-Groups Design

  17. Solomon Four-Group Design

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