1. A diagnostic apparatus for diagnosing a measured object based on time-series data of a plurality of parameters from the measured object, comprising: a computer including a processor, a memory and a recording medium, wherein the recording medium causes the processor to diagnose a measured object based on time-series data of a plurality of parameters from the measured object, wherein the recording medium comprises: a change-point score calculating portion for calculating a time-series change-point score with which each parameter of the plurality of parameters changes according to passage of time based on the time-series data on said each parameter; a change-point correlation calculating portion for calculating a change-point correlation indicating strength by which each of the plurality of parameter is associated with each of other parameters based on the change-point scores of said each parameter and the other parameter; and a parameter outputting portion for outputting a set of parameters of which calculated degrees of associations are high than a predetermined reference change-point correlation, said set being mutually strongly associated parameters, wherein the parameter outputting portion, when a particular parameter having caused trouble is specified by a user, outputs a set of the parameters for which degrees of associations with the particular parameter are higher than the reference degree of association; the change-point score calculating portion calculates the time-series charge point score with which each of the plurality of parameters having mutually different units changes according to the passage of time; the change-point correlation calculating portion normalizes the change-point score of each parameter to form a normalized change-point score of each parameter, so that an integral of the change-point score of each parameter becomes a predetermined unit quality in a predetermined measurement period; the normalized change-point score of the parameter and the normalized change-point score of the other parameter being delayed by a predetermined delay time against the parameter are regarded as objects for comparison so as to calculated a maximum value of the change-point correlation based on comparisons made by sequentially changing the delay time in the predetermined range; and the parameter output portion outputs, among the parameter whose change-point correlation with the parameter specified by the user, a parameter whose change-point correlation is higher than the reference change-point correlation by delaying compared to the parameter specified by the user.