The width (Delta nu) and root mean squared amplitude (r(S)) of lower and upper kHz quasi-periodic oscillations (QPOs) from accreting neutron stars vary with frequency. Similarly, the QPO frequency varies with the source count rate (S). Hence, the significance of a QPO, scaling as S x r(S)(2)/root Delta nu, will also depend on frequency. In addition, the significance also scales up with the square root of the integration time of the Fourier power-density spectrum (T). In practice and in most analysis, Tis constrained (e. g. limited by the Rossi X-ray Timing Explorer (RXTE) orbital period if the source is occulted by the Earth) or minimized to increase the number of detections.