a cohen's d of –0.19 is the type of effect size of small.
a cohen's d of –0.19 is what type of effect size?
small
length noted for a "medium" effect size, "you'll choose the same "n" regardless of the accuracy or reliability of your instrument, or the narrowness or diversity of your subjects. clearly, important considerations are being ignored here. researchers should interpret the substantive significance of their results by grounding them in a meaningful context or by quantifying their contribution to knowledge, and cohen's effect size descriptions can be helpful as a starting point." similarly, a u.s. dept of education sponsored report said "the widespread indiscriminate use of cohen’s generic small, medium, and large effect size values to characterize effect sizes in domains to which his normative values do not apply is thus likewise inappropriate and misleading."
effect size
an effect size related to the common language effect size is the rank-biserial correlation. this measure was introduced by cureton as an effect size for the mann–whitney "u" test. that is, there are two groups, and scores for the groups have been converted to ranks. the kerby simple difference formula computes the rank-biserial correlation from the common language effect size. letting f be the proportion of pairs favorable to the hypothesis (the common language effect size), and letting u be the proportion of pairs not favorable, the rank-biserial r is the simple difference between the two proportions: "r" = "f" − "u". in other words, the correlation is the difference between the common language effect size and its complement. for example, if the common language effect size is 60%, then the rank-biserial r equals 60% minus 40%, or "r" = 0.20. the kerby formula is directional, with positive values indicating that the results support the hypothesis.
effect size