1. An information analysis apparatus for performing an analysis on text information to determine whether or not the text information corresponds to target information, comprising: a storage device that stores the text information; a density estimation unit that estimates, in units of analysis each composed of a plurality of sentences of the text information, a density indicating a degree to which each unit of analysis contains the target information; and a determination unit that obtains an evaluation value indicating a degree to which each sentence included in each unit of analysis corresponds to the target information from the estimated density of the unit of analysis, and determines whether or not the sentence is the target information based on the evaluation value.
1. An information analysis apparatus for performing an analysis on text information to determine whether or not the text information corresponds to target information, comprising: a storage device that stores the text information; a density estimation unit that estimates, in units of analysis each composed of a plurality of sentences of the text information, a density indicating a degree to which each unit of analysis contains the target information; and a determination unit that obtains an evaluation value indicating a degree to which each sentence included in each unit of analysis corresponds to the target information from the estimated density of the unit of analysis, and determines whether or not the sentence is the target information based on the evaluation value. 11. The information analysis apparatus according to claim 1 , further comprising: a training data generation unit that generates training data from training text information; and a density estimation model learning unit, wherein the training text information includes information indicating whether or not each sentence of the training text information is the target information, and has generated therein a plurality of units of training each composed of a plurality of sentences of the training text information, the training data generation unit sets, for each unit of training, a target information density indicating a degree to which the unit of training contains the target information, with reference to information indicating whether or not each sentence of the unit of training is the target information, further obtains, for each unit of training, a feature quantity from information acquired from a word or a clause in each sentence of the unit of training, and generates the target information density and the feature quantity of each unit of training as the training data, the density estimation model learning unit learns a density estimation model usable in the density estimation performed by the density estimation unit, using the generated training data, and the density estimation unit estimates the density for each unit of analysis in accordance with the density estimation model learned by the density estimation model learning unit.