Q:

# What does "effect size" mean?

A:

In statistics, effect size is the magnitude of the difference between two variables. The most common measures of effect size used are the correlation coefficient "r" and the regression coefficient "R."

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The correlation coefficient "r" is commonly used in statistics to measure effect size because it can be used to indicate any possible relationship strength between variables. An "r" value of zero indicates that the variables have no relationship at all, while if the absolute value of "r" is 1, the variables are in perfect correlation.

In terms of effect size, if the absolute value of "r" is 0.1, then the variables have a small effect size. If it is 0.3, then the variables have a medium effect size. If it is 0.5, then the variables have a large effect size.

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