Host star metallicities vs. planet orbital period (grey dots) from the synthetic sample. The red line denotes the kernel regression of the mean metallicity of the planet population (from Equation (16)). The shaded red area shows the 68% (1-σ) confidence interval on the mean from bootstrapping. The dashed black line represents the mean metallicity (−0.05 ± 0.04 dex) for stars that host planets with a period >ten days. In the bottom-left corner, we print the Pearson coefficient R between host star metallicity and the orbital periods as well as the correspond p–value.