请问，多分类logistic回归，由于因变量部分类别收集到的人数太少，最后的结果发现该类别的OR值特别小，这会影响其他类别结果的可靠性吗？是否表示其他类别的结果也不可靠。spss运行后出现了warnings：Unexpected singularities in the Hessian matrix are encountered. This indicates that either some predictor variables should be excluded or some categories should be merged.The NOMREG procedure continues despite the above warning(s). Subsequent results shown are based on the last iteration. Validity of the model fit is uncertain.