This article provides a simplified methodology for calculating Cohen's d, η^2 and ω^2 effect sizes from published experiments that use t-tests and F-tests. Whereas statistical tests of significance tell us the likelihood that experimental results differ from chance expectations, effect-size measurements tell us the relative magnitude of the experimental treatment. They tell us the size of the experimental effect. Effect sizes are especially important because they allow us to compare the magnitude of experimental treatments from one experiment to another.