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