<p>Based on observations from Parker Solar Probe, this paper studies the dependence of the correlations between the transition-range spectral index of the magnetic energy spectrum and four parameters (inertial-range cross-helicity and magnetic energy density, transition-range magnetic helicity, and bulk proton temperature) on solar wind speed and heliocentric distance. Results show significant correlations between the spectral index and both cross-helicity and magnetic energy density. Notably, at lower speeds or closer distances, the correlation coefficient (CC) between the cross-helicity and spectral index is smaller than that between the magnetic energy density and spectral index. Conversely, at higher speeds or greater distances, the correlation with cross-helicity becomes comparable to or even exceeds that with magnetic energy density. Additionally, as the speed increases or the heliocentric distance decreases, cross-helicity, magnetic energy density, proton temperature, and the absolute values of the spectral index show a mostly upward trend. Moreover, cross-helicity, absolute values of the spectral index, and CC between the magnetic energy density and spectral index exhibit a similar trend with the speed, initially rising and then declining at the highest speed bin. We discuss the results using the recently proposed “helicity barrier” effect.</p>