  The one-fifth success rule is one of the best-known and most widely accepted
techniques to control the parameters of evolutionary algorithms. While it is
often applied in the literal sense, a common interpretation sees the one-fifth
success rule as a family of success-based updated rules that are determined by
an update strength $F$ and a success rate. We analyze in this work how the
performance of the (1+1) Evolutionary Algorithm on LeadingOnes depends on these
two hyper-parameters. Our main result shows that the best performance is
obtained for small update strengths $F=1+o(1)$ and success rate $1/e$. We also
prove that the running time obtained by this parameter setting is, apart from
lower order terms, the same that is achieved with the best fitness-dependent
mutation rate. We show similar results for the resampling variant of the (1+1)
Evolutionary Algorithm, which enforces to flip at least one bit per iteration.
