  Nearly $1.32 \times 10^6$ sec of non-zero count rate data were obtained from
five years of {\rm RXTE} observations of the atoll source 4U 1636-53. The data
was divided into 10309 segments of 128 sec each. The histogram of the number of
segments as a function of count rate shows that the system can naturally be
classified into four flux states. For each segment an automated search for kHz
QPO was undertaken and the histograms of the maximum Leahy normalised power
$P_{max}$ for the four flux states were created. These were fitted by
probability distribution functions under the assumption that the intrinsic
amplitude of the QPO has a normal distribution. The best fit distribution
functions, showed that the fraction $f$ of the time the system exhibits a kHz
QPO, decreases from near unity for the lowest flux state ($\approx 1400$ c/s)
to zero for the highest one ($> 2550$ c/s) while the average amplitude remains
nearly constant. Based on the best fit probability distribution functions, a
threshold $P_{thre}$ was defined, such that 95% of the segments with $P_{max} >
P_{thre}$ correspond to a real QPO signal. For segments selected by this
criterion, the frequency versus count rate plot reproduced the earlier known
``parallel track'' variation with the tracks coinciding roughly with the flux
states. It is shown that the gaps between the tracks are not caused by uneven
sampling, but rather the QPO phenomenon is absent or weak when the system's
flux level is intermediate between two flux states.
