Table 3: Comparison of the velocity dispersions derived in this study and in previous works. The table columns are: Offset: mean offset between this study and the one in Col. 1; rms: dispersion among the mean value; Exp. rms: dispersion expected from the errors; z: result of a z-test to contrast the hypothesis of a null offset (a value higher than 1.96 allows us to reject the hypothesis with a significance level lower than 0.05); N: number of galaxies in each comparison. Units are km s^-1.

Study	Offset	rms	Exp. rms	z	N
G93	12.5	19.5	9.6	3.1	33
T98	13.7	15.1	10.7	4.8	52
M02	17.4	21.2	11.0	1.7	12
K01	12.9	15.8	11.9	3.5	31