In a method of determining a regression model, and a method of predicting a component concentration of a test mixture using the regression model, the method of determining the regression model includes selecting a regression model, generating a plurality of observation points, each one of the plurality of observation points having a prediction target value and a measured value, determining a weight of the prediction target value and the measured value at each one of the plurality of observation points, and obtaining a calculation amount by reflecting the weights in differences between predicted values acquired by applying the measured values to the regression model and the prediction target values, and determining coefficients of the regression model to minimize the calculation amount.