  We propose a model-independent scaling method to study the physical
properties of high-temperature superconductors in the normal state. We have
analyze the experimental data of the c-axis resistivity, the in-plane
resistivity, the Hall coefficient, the magnetic susceptibility, the
spin-lattice relaxation rate, and the thermoelectric power using this method.
It is shown that all these physical quantities exhibit good scaling behaviors,
controlled purely by the pseudogap energy scale in the normal state. The doping
dependence of the pseudogap obtained from this scaling analysis agrees with the
experimental results of angle-resolved photoemission and other measurements. It
sheds light on the understanding of the basic electronic structure of high-Tc
oxides.
