Estimating Magnitude of Effect

  1. What is R2?
    • The variability accounted for by the full model
    • The sum of squares for the model divided by the SS total
  2. How might one express the magnitude of effect?
    • 1) Find the R2
    • 2) Express the difference in means and SD
  3. How might one express the difference between the means and SD of two data sets
    • The means must be compared in SD units 
    • Cohen's D is employed
  4. What is the formula for independent group Cohen's D?
    Mean 1- mean 2 divided by the standard deviation of the scores (or residuals)
  5. How can we estimate d values?
    If population means or SD are not known we replace the parameter values with their corresponding statistics
  6. What is a small effect size?
  7. What is a medium effect size?
  8. What is a large effect size?
  9. What is the d value used for?
    • As a descriptive statistic (provides an index that can be used to compare effect sizes across different experiments)
    • Deciding upon sample sizes 
    • Estimating power
  10. What is experimental precision?
    • The amount of variability in true parameter estimates
    • The less variability, the greater the precision
  11. How can we increase experimental precision?
    • Reduce the size of standard error 
    • The best way of doing this is to increase sample size
Card Set
Estimating Magnitude of Effect