Given a finite group G, let P G (s) be the probability that s randomly chosen elements generate G, and let H be a finite group with P G (s) = P H (s). We show that if the nonabelian composition factors of G and H are PSL(2, p) for some non-Mersense prime p ≥ 5, then G and H have the same non-Frattini chief factors.2010 Mathematics Subject Classification. 20D06.