Interpreting Effect Size (d)
l Cohen (1977):   .2     = small
                                  .5     = moderate
                                  .8     = large
l Wolf (1986):       .25     = educationally
               significant
                                  .50     = practically signficant
               (therapeutic)
l ESs are proportional, e.g.,
        .40 is twice as much change as .20