Imagine

a researcher interested in establishing whether religious people differ in

illusory pattern perceptions from non-religious people (i.e., religion would be

the independent variable). Illusionary pattern perception was measured on a

10-point Likert scale. On face value, the illusory pattern perception of

non-religious people was, on average (M = 4.97, SD = 3.66, n = 52), lower than that

of religious people (M = 5.97, SD = 2.43, n = 48). To test for mean differences

in two independent groups, the researcher conducted an independent samples

t-test and estimated a t- value of 4.85 with an associated p-value of p =

0.0003 and the effect size of Cohen’s d = 0.321. What does Cohen’s d tell us?