Histograms of (a) the standard deviation of the fits σ_fit and (b) the number of data points Ndat for our Cepheid sample. Histogram of uncertainties of low-order Fourier parameters are displayed for (c) σ(ϕ₂₁), (d) σ(R₂₁), (e) σ(ϕ₃₁), and (f) σ(R₃₁) for Cepheids of this paper and, for comparison, for Cepheids from Storm et al. (2011). In each plot, the median of each sample is represented by a vertical dashed line. See Sect. 3.