But there is no riskless asset in reality, so zero beta CAPM may be a better model. Thus the test is more complicated, because the hypothesis to be tested is nonlinear.

• 然而现实的市场不存在无风险资产,零贝塔CAPM针对此假设对CAPM进行了修正,但是得出的约束条件不再是线性,因此检验变得复杂。