In a small sample of 20 subjects, three continuous independent variables significantly predict a dichotomous dependent variable (Method = Enter, SPSS). Step 0 (constant) is not significant, but all three variables not in the equation are. Step 1 (Block and Model) are significant Chi (3) = 12.665, p = .005, percentage correct = 90% (very high). But in the last table, no variable in the equation (neither the constant nor the three independent ones) presents a statistically significant coefficient, and Exp (B) are very small: between 0.872 and 1.620. The results are incongruous to me, how should I interpret them?

Thanks

Matt