  We study the dependence of kHz quasi-periodic oscillation (QPO) frequency on
accretion-related parameters in the ensemble of neutron star low-mass X-ray
binaries. Based on the mass accretion rate, $\dot{M}$, and the magnetic field
strength, $B$, on the surface of the neutron star, we find a correlation
between the lower kHz QPO frequency and $\dot{M}/B^{2}$. The correlation holds
in the current ensemble of Z and atoll sources and therefore can explain the
lack of correlation between the kHz QPO frequency and X-ray luminosity in the
same ensemble. The average run of lower kHz QPO frequencies throughout the
correlation can be described by a power-law fit to source data. The simple
power-law, however, cannot describe the frequency distribution in an individual
source. The model function fit to frequency data, on the other hand, can
account for the observed distribution of lower kHz QPO frequencies in the case
of individual sources as well as the ensemble of sources. The model function
depends on the basic length scales such as the magnetospheric radius and the
radial width of the boundary region, both of which are expected to vary with
$\dot{M}$ to determine the QPO frequencies. In addition to modifying the length
scales and hence the QPO frequencies, the variation in $\dot{M}$, being
sufficiently large, may also lead to distinct accretion regimes, which would be
characterized by Z and atoll phases.
