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Lecture 12 - Chapter 12

Lecture 12 - Chapter 12. Factorial Design (Multifactor). More than one IV. Most frequently used design. Terminology. IV = Factors. One way…. Two way, Three way …. Why?. In real world/natural setting not Just one variable impacts behavior! Variables combine to impact behavior.

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Lecture 12 - Chapter 12

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  1. Lecture 12 - Chapter 12 Factorial Design (Multifactor) More than one IV Most frequently used design Terminology IV = Factors One way…. Two way, Three way …

  2. Why?

  3. In real world/natural setting not Just one variable impacts behavior! Variables combine to impact behavior Interact  interaction

  4. Interaction: the effect of one Factor (IV) on the DV changes depending on the level of the other factor (IV) Artificial variable weather & temperature Running speed

  5. Design Notation: Matrix of Cells How many Factors (IVs) How many levels 2 X 2 3 X 2 5 X 2 Levels of A Levels of A Levels of A Levels of B Levels of B Levels of B

  6. Testing more than one • Hypothesis • No difference bwt • the levels of A • If difference… • MAIN EFFECT • No difference bwt • the levels of B • If difference… • MAIN EFFECT • 3. No significant • interaction of factor • A & B…signif interaction

  7. Possible Outcomes

  8. Possible Outcomes

  9. Whether you are using a t-test, one-way ANOVA, Factorial • Did you get an effect???? • Significance level  (p value) • Ex: F ratio…you found sign. • difference and with 95% confidence (0.05) not just • due to chance • and F ratio represents  F= 67.01…67 times more • variance between the groups than • expected by chance • …very dependent on sample size…power • Large F may represent sample size…so..

  10. We need some measure that • Index of the STRENGHT of the • experimental effect • 2. Independent of Sample Size Effect Size (Magnitude of Effect) Proportion of the variance “explained”, “accounted” for by the treatment… “treatment effect”… Does this ring a bell

  11. Whether you are using a t-test, one-way ANOVA, Factorial Effect Size: Partial Eta Squared (h2p) SS Main Effect or Interaction / SS Main Effect or Interaction+SS Error …notice n not a part of the formula Number ranges from .00 to 1.00 (correlation between the effect and the DV) Small:? Med:? Large:? Depends on the area of interest .40 .25 .10 ANOVA t-test

  12. Other tests out there in the world… Extension of ANOVA MANOVA: Multivariate Analysis More than one DV

  13. Examples… For the main effect of ATTRACT partial Eta squared was .90, therefore the variable of ATTRACT accounted for 90% of the overall (effect+error) variance. 30 % of the variation in time spent in conversation can be attributed to the type of the approach… The interaction accounted for 41% of the total variance….

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