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New laboratory measurements using an Electron Beam Ion Trap (EBIT) and anx-ray microcalorimeter are presented for the n=3 to n=2 Fe XVII emission linesin the 15 {\AA} to 17 {\AA} range, along with new theoretical predictions for avariety of electron energy distributions. This work improves upon our earlierwork on these lines by providing measurements at more electron impact energies(seven values from 846 to 1185 eV), performing an in situ determination of thex-ray window transmission, taking steps to minimize the ion impurityconcentrations, correcting the electron energies for space charge shifts, andestimating the residual electron energy uncertainties. The results for the3C/3D and 3s/3C line ratios are generally in agreement with the closest theoryto within 10%, and in agreement with previous measurements from an independentgroup to within 20%. Better consistency between the two experimental groups isobtained at the lowest electron energies by using theory to interpolate, takinginto account the significantly different electron energy distributions.Evidence for resonance collision effects in the spectra is discussed.Renormalized values for the absolute cross sections of the 3C and 3D lines areobtained by combining previously published results, and shown to be inagreement with the predictions of converged R-matrix theory. This workestablishes consistency between results from independent laboratories andimproves the reliability of these lines for astrophysical diagnostics. Factorsthat should be taken into account for accurate diagnostics are discussed,including electron energy distribution, polarization, absorption/scattering,and line blends.

Fe XVII X-ray Line Ratios for Accurate Astrophysical Plasma Diagnostics