12. The information analysis apparatus according to claim 2 , 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, the training data generation unit generates a plurality of units of training each composed of a plurality of sentences of the training text information, from the training text information in accordance with a setting condition, sets, for each unit of training, a target information density indicating an amount of the target information included in the unit of training, 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.
14. The information analysis apparatus according to claim 12 , wherein the training data generation unit generates the plurality of units of training by, for each unit of training, extracting a preset number of consecutive sentences from a plurality of consecutive sentences of the training text information and generating the unit of training from the extracted consecutive sentences, and further obtains, for each unit of training, a feature quantity from one or more types of information that include information acquired from a word or a clause in each sentence of the unit of training and information acquired by comparing the training text information and each sentence of the unit of training.