Effect size
= Effect size
{wiki}
An <effect size> measures the magnitude of an observed or modeled relationship. A <standardized mean difference> expresses a mean contrast in standard-deviation units; other <effect sizes> include a <correlation coefficient> or <odds ratio>. Magnitude is distinct from the evidence against a <null hypothesis> supplied by a <p-value>: a small <effect size> can have a small <p-value> in a sufficiently large sample.