A system and method are provided for creating a network performance prediction model, and calibrating the prediction model, through application of network load statistical analyses. Preferably, the sensor device is encapsulated to protect the components from the environment. The productive state is a pseudo-senescent state. The bending portion has a narrow width in order to occupy small space of a rear wall of the housing member so that the rear wall of the housing member still has adequate area for mounting other components. The cleaning blade is formed of a material whose tensile stress-elongation test shows that the definite integral of a tensile stress with respect to an elongation percentage on an interval between the elongation percentage of zero and the elongation percentage at which the stress is a predetermined value is a predetermined upper limit value or less.