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Estimating Magnitude of Effect
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What is R
^{2}
?
The variability accounted for by the full model
The sum of squares for the model divided by the SS total
How might one express the magnitude of effect?
1) Find the R
^{2}
2) Express the difference in means and SD
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
What is the formula for independent group Cohen's D?
Mean 1- mean 2 divided by the standard deviation of the scores (or residuals)
How can we estimate d values?
If population means or SD are not known we replace the parameter values with their corresponding statistics
What is a small effect size?
0.20
What is a medium effect size?
0.50
What is a large effect size?
0.80
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
What is experimental precision?
The amount of variability in true parameter estimates
The less variability, the greater the precision
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
Description
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Updated
2015-02-27T14:02:35Z
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