lesson 2 (expepsych)

• Effect Size


  Statistical estimate of the size or magnitude of the treatment effect
• One Independent Variable: Two Groups Design

  • Two-independent groups variable
  • Two matched groups design
• Random Assignment


  Means that every subject has an equal chance of being placed in any of the treatment conditions
• Control Group


  Used to determine the value of the dependent variable without an experimental manipulation of the independent variable
• Experimental Group


  We apply a particular value of our independent variable and measure the dependent variable
• Two-Experimental Groups Design


  Can be used to look at the behavioral differences that occur when subjects are exposed to two different values or level of your independent variable
• When to use a Two-Independent Groups Design


  1. Begin by looking at the hypothesis

  2. We assume that randomization is successful
• Two Matched Groups Design

  • Precision Matching
  • Range Matching
  • Rank-Ordered Matching
• Random Table


  A list of numbers that can be used to generate numbers to stimulate experiments
• Choosing Treatments


  1. Condition must be proportional

  2. Always think about your hypothesis: what will you gain by adding extra conditions to the experiment

  3. General rule: select the most simplest design that will make an adequate test of your hypothesis
• Factorial Design


  Design in which we study two or more independent variables at the same time
• Factors


  Independent variable
• Two-Factor Experiment (2x2)


  Simplest factorial design
• Main Effects


  The action of a single independent variable
• Interactions


  An interaction is present if the effect of one independent variable changes across the levels of another independent variable
• Higher Order Interactions


  Can be produced in experiments with more than two factors
• Shorthand and Notation


  Tell us several things about the experiment it describes
• Practical reason for keeping factorial designs simple: Subjects are usually assigned to each treatment conditions at random
• Possible Effects of Two Factor Between Subjects Design

  • Main effect for each factor
  • Interaction between the two factors