Discrimination index (DI), also called point biserial
correlation (PBS), describes the ability of an item to distinguish between high and low scorers.9 It ranges between -1.00 and +1.00.
The members of this genus (formerly known as Glyphidodontops Bleeker, 1877) are relatively elongate (2.1-2.7 in SL for most species, although the complex of species treated herein usually 1.9-2.2 in SL) pomacentrids, with smooth preopercular and suborbital margins, and most species possess biserial
The point biserial
correlation between the two dominance estimates was significant (r=0.375; p<0.005).
A Pearson r correlation indicated the strength of significant relationships between developmental status and efficacy (r = -.46, p [is less than] .001) and between developmental status and performance (r = -.27, p = .01) (Note: Pearson r is mathematically equivalent to a point biserial
r when the second variable is dichotomous).
However, as the dependent variable is binary, and the logit score is a continuous variable, to allow comparison with personnel research which assesses validity in terms of the validity coefficient r, the (conservative) point biserial
correlation coefficient ([r.sub.pbi) for the model is also provided (Guilford & Fruchter, 1984).
A point biserial
correlation was used to test significance of the relationship between the level of family stress scores and perception of pregnancy ratings (rpb = .13, p = .22).
For each card a point biserial
correlation was computed between the selection (1 or 0) and the inspection time across the 30 subjects.
The t-test of 7.17 converts to a point biserial
correlation of .47.
The third column of Table 3 presents the average item difficulty of each of the subtests, and the fourth column presents the average item-total, or point biserial
, correlations for each subtest.