Many of the individual characteristics measured in risk studies co-vary with other individual differences.
风险研究中测量的很多个体特征和其它的个体差别一起变动。
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The method is used when the model is complex and nonlinear (that is, parameters do not co-vary in a linear manner), or when the model involves more than just two or three uncertain parameters.
The steps to incorporate vary, depending on whether your group is just starting out or is already an unincorporated association, a co-operative or a company.