1. A calibration curve creating method of creating a calibration curve used in acquiring content of a target component of a test object from observation data of the test object, the method comprising: (a) causing a computer to acquire the observation data of a plurality of samples of the test object; (b) causing the computer to acquire content of the target component of each sample; (c) causing the computer to estimate a plurality of independent components when the observation data of each sample is separated into the plurality of independent components, and to acquire a mixing coefficient corresponding to the target component for each sample, based on the plurality of independent components; and (d) causing the computer to acquire a regression equation of the calibration curve based on the content of the target component of the plurality of samples and the mixing coefficient for each sample, wherein (c) includes (i) causing the computer to acquire an independent component matrix including the independent component of each sample, (ii) causing the computer to acquire an estimated mixing matrix showing a vector set for regulating a ratio of an independent component element of each independent component in each sample, from the independent component matrix, and (iii) causing the computer to acquire a correlation of content of the target component of the plurality of samples, for each vector included in the estimated mixing matrix, and to select the vector which is determined to have a highest correlation, as a mixing coefficient corresponding to the target component, in (i), the computer acquires the independent component matrix by performing a first preprocessing including normalization of the observation data, a second preprocessing including whitening, and an independent component analysis process in this order, the computer uses β divergence as an independence index of the independent component analysis process, and a robust regression method is used in (d) acquiring the regression equation of the calibration curve.