Planet-metallicity correlation observed in our Lick sample, ignoring the effect of stellar mass on the planet occurrence rate. The filled histogram shows secure planets, whereas the open histogram includes planet candidates as well. Error bars are computed based on binomial statistics as explained in the text. The solid line illustrates the exponential fit to the planet occurrence rate of secure planets as a function of metallicity, for a stellar mass of 1.9  M_⊙. The black dots also correspond to the exponential fit, but here the individual mass distribution in each bin has been taken into account.