Normalized Mandel Parameter is introduced as a new measurement of photon statistics. Dependences of Mandel parameter Q and corresponding normalized Mandel parameter on photon-counting time interval are experimentally investigated for pseudo-thermal light. We demonstrate that is more appropriate than Q to measure the statistical deviation from Poisson distribution, because presents clearly both the intrinsic statistical properties and measuring effects. The advantages of in charactering nonclassical emissions are also discussed.
