# Estimating Magnitude of Effect

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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?
0.20
7. What is a medium effect size?
0.50
8. What is a large effect size?
0.80
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
 Author: camturnbull ID: 297015 Card Set: Estimating Magnitude of Effect Updated: 2015-02-27 14:02:35 Tags: Stats Folders: Stats Description: . Show Answers: