1. A server for communicating with a plurality of monitoring devices via a network, each monitoring device acquiring monitoring variables (1˜H; H is an integral number larger than 1) from an observation target and generating an individual multidimensional distribution of the monitoring variables, the server comprising: a receiving unit configured to collect the individual multidimensional distribution from each monitoring device, a first space defined by axes of the monitoring variables (1˜H) being divided into a plurality of first elements at each monitoring device, the individual multidimensional distribution representing a probability density or a frequency of the monitoring variables belonging to each first element in the first space; a first server side generation unit configured to generate first sampling data by sampling the individual multidimensional distribution collected, to determine a first discretion parameter using the first sampling data so that a first evaluation function including the first discretion parameter is maximized or minimized, the first discretion parameter indicating a method for dividing the first space, to divide the first space into a plurality of second elements by the first discretion parameter, and to generate an overall multidimensional distribution representing a probability density or a frequency of the first sampling data belonging to each second element in the first space; a statistical estimation unit configured to determine a model parameter of statistical models (1˜K; K is an integral number larger than 1) using the overall multidimensional distribution so that a second evaluation function including the model parameter is maximized or minimized, the model parameter being used for calculating indexes (1˜K) to evaluate a state of each observation target from the monitoring variables; a second server side generation unit configured to generate a second sampling data by sampling the overall multidimensional distribution, to calculate index data of the indexes (1˜K) by calculating the statistical models with the second sampling data, to determine a second discretion parameter using the index data so that a third evaluation function including the second discretion parameter is maximized or minimized, the second discretion parameter indicating a method for dividing a second space defined by axes of the indexes (1˜K), to divide the second space into a plurality of third elements by the second discretion parameter, and to generate an overall index multidimensional distribution representing a probability density or a frequency of the index data belonging to each third element in the second space; and a transmission unit configured to transmit the overall index multidimensional distribution and the statistical models (1˜K) having the model parameter to each monitoring device.