1. A status monitor apparatus, comprising: a collection unit to collect data relating to the status of an object to be monitored in a time series; a calculation unit to calculate fluctuation of data obtained by said collection unit; an extraction unit to apply an adaptive lattice filter to the fluctuation calculated by said calculation unit, and to extract normal white noise component corresponding to the fluctuation from among parameters appearing in a calculating process of the adaptive lattice filter; a detection unit to detect a change in status of the object to be monitored based on behavior of the normal white noise component extracted by said extraction unit; an estimation unit to estimate the number of samples for a statistical test based on a forgetting factor used in the adaptive lattice filter, wherein said detection unit includes a first decision unit to decide whether or not the variance of the normal white noise component is within a scone determined based on a reference value by the statistical test of the estimated number of samples; and a second decision unit to decide whether or not the status of the object to be monitored has changed based on a decision result by said first decision unit.