We begin by establishing the unbiasedness of ols estimators under a set of assumptions 首先，我们在一些假定下证明ols估计量的无偏性。
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The conclusion is that the back analysis results have the character of unbiasedness , efficiency and consistency . bayes random method which considers the prior errors is better in the back analysis of embankment dam ' s nonlinear materials 结论认为bayes随机反演结果具有无偏性、有效性和一致性的特点；在土石坝等非线性材料反演分析中，考虑先验信息误差的bayes随机反分析方法具有较好的适用性。
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In the third section three different forms of heteroscedasticity are used in the random simulation and then park test , glejser test and goldfeld - quandt test are compared although the existence of heteroscedasticity does not destroy the unbiasedness of the ols estimators , the variances become larger 异方差的存在虽然并不破坏普通最小二乘估计量的无偏性，但是估计量的方差变大了。由于估计量方差的变大，就使通常假设检验的值不可靠。
